{"id":5257,"date":"2021-08-08T22:37:23","date_gmt":"2021-08-08T14:37:23","guid":{"rendered":"https:\/\/www.xttblog.com\/?p=5257"},"modified":"2021-08-08T22:37:23","modified_gmt":"2021-08-08T14:37:23","slug":"mysql8%e4%b8%ad%e6%96%b0%e5%a2%9e%e4%ba%86%e4%b8%89%e5%a4%a7%e7%b4%a2%e5%bc%95%ef%bc%8c%e9%9a%90%e8%97%8f%e7%b4%a2%e5%bc%95%e3%80%81%e9%99%8d%e5%ba%8f%e7%b4%a2%e5%bc%95%e3%80%81%e5%87%bd%e6%95%b0","status":"publish","type":"post","link":"https:\/\/www.xttblog.com\/?p=5257","title":{"rendered":"MySQL8\u4e2d\u65b0\u589e\u4e86\u4e09\u5927\u7d22\u5f15\uff0c\u9690\u85cf\u7d22\u5f15\u3001\u964d\u5e8f\u7d22\u5f15\u3001\u51fd\u6570\u7d22\u5f15"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">\u4eca\u5929\u6211\u4eec\u4e00\u8d77\u6765\u804a\u804a MySQL 8.x \u7248\u672c\u4e2d\u65b0\u589e\u7684\u4e09\u5927\u7d22\u5f15\u3002MySQL 8.x \u4e2d\u65b0\u589e\u4e86\u4e09\u79cd\u7d22\u5f15\u65b9\u5f0f\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u9690\u85cf\u7d22\u5f15<\/li><li>\u964d\u5e8f\u7d22\u5f15<\/li><li>\u51fd\u6570\u7d22\u5f15<\/li><\/ul>\n\n\n\n<div class=\"wp-block-image\"><figure class=\"aligncenter\"><img decoding=\"async\" src=\"https:\/\/cdn.jsdelivr.net\/gh\/xmt1139057136\/xttblog\/2021\/08\/mysql8.jpg\" alt=\"\" \/><figcaption>MySQL8\u65b0\u7279\u6027<\/figcaption><\/figure><\/div>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e00\u3001\u9690\u85cf\u7d22\u5f15<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1.\u9690\u85cf\u7d22\u5f15\u6982\u8ff0<\/h3>\n\n\n\n<ul class=\"wp-block-list\"><li>MySQL 8.0 \u5f00\u59cb\u652f\u6301\u9690\u85cf\u7d22\u5f15\uff08invisible index\uff09\uff0c\u4e0d\u53ef\u89c1\u7d22\u5f15\u3002<\/li><li>\u9690\u85cf\u7d22\u5f15\u4e0d\u4f1a\u88ab\u4f18\u5316\u5668\u4f7f\u7528\uff0c\u4f46\u4ecd\u7136\u9700\u8981\u8fdb\u884c\u7ef4\u62a4\u3002<\/li><li>\u5e94\u7528\u573a\u666f\uff1a\u8f6f\u5220\u9664\u3001\u7070\u5ea6\u53d1\u5e03\u3002<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u5728\u4e4b\u524d MySQL \u7684\u7248\u672c\u4e2d\uff0c\u53ea\u80fd\u901a\u8fc7\u663e\u5f0f\u7684\u65b9\u5f0f\u5220\u9664\u7d22\u5f15\uff0c\u5982\u679c\u5220\u9664\u540e\u53d1\u73b0\u7d22\u5f15\u5220\u9519\u4e86\uff0c\u53c8\u53ea\u80fd\u901a\u8fc7\u521b\u5efa\u7d22\u5f15\u7684\u65b9\u5f0f\u5c06\u5220\u9664\u7684\u7d22\u5f15\u6dfb\u52a0\u56de\u6765\uff0c\u5982\u679c\u6570\u636e\u5e93\u4e2d\u7684\u6570\u636e\u91cf\u975e\u5e38\u5927\uff0c\u6216\u8005\u8868\u6bd4\u8f83\u5927\uff0c\u8fd9\u79cd\u64cd\u4f5c\u7684\u6210\u672c\u975e\u5e38\u9ad8\u3002\u5728 MySQL 8.0 \u4e2d\uff0c\u53ea\u9700\u8981\u5c06\u8fd9\u4e2a\u7d22\u5f15\u5148\u8bbe\u7f6e\u4e3a\u9690\u85cf\u7d22\u5f15\uff0c\u4f7f\u67e5\u8be2\u4f18\u5316\u5668\u4e0d\u518d\u4f7f\u7528\u8fd9\u4e2a\u7d22\u5f15\uff0c\u4f46\u662f\uff0c\u6b64\u65f6\u8fd9\u4e2a\u7d22\u5f15\u8fd8\u662f\u9700\u8981 MySQL \u540e\u53f0\u8fdb\u884c\u7ef4\u62a4\uff0c\u5f53\u786e\u8ba4\u5c06\u8fd9\u4e2a\u7d22\u5f15\u8bbe\u7f6e\u4e3a\u9690\u85cf\u7d22\u5f15\u7cfb\u7edf\u4e0d\u4f1a\u53d7\u5230\u5f71\u54cd\u65f6\uff0c\u518d\u5c06\u7d22\u5f15\u5f7b\u5e95\u5220\u9664\u3002\u8fd9\u5c31\u662f\u8f6f\u5220\u9664\u529f\u80fd\u3002 \u7070\u5ea6\u53d1\u5e03\uff0c\u5c31\u662f\u8bf4\u521b\u5efa\u7d22\u5f15\u65f6\uff0c\u9996\u5148\u5c06\u7d22\u5f15\u8bbe\u7f6e\u4e3a\u9690\u85cf\u7d22\u5f15\uff0c\u901a\u8fc7\u4fee\u6539\u67e5\u8be2\u4f18\u5316\u5668\u7684\u5f00\u5173\uff0c\u4f7f\u9690\u85cf\u7d22\u5f15\u5bf9\u67e5\u8be2\u4f18\u5316\u5668\u53ef\u89c1\uff0c\u901a\u8fc7 explain \u5bf9\u7d22\u5f15\u8fdb\u884c\u6d4b\u8bd5\uff0c\u786e\u8ba4\u8fd9\u4e2a\u7d22\u5f15\u6709\u6548\uff0c\u67d0\u4e9b\u67e5\u8be2\u53ef\u4ee5\u4f7f\u7528\u5230\u8fd9\u4e2a\u7d22\u5f15\uff0c\u5c31\u53ef\u4ee5\u5c06\u5176\u8bbe\u7f6e\u4e3a\u53ef\u89c1\u7d22\u5f15\uff0c\u5b8c\u6210\u7070\u5ea6\u53d1\u5e03\u7684\u6548\u679c\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">2.\u9690\u85cf\u7d22\u5f15\u64cd\u4f5c<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\uff081\uff09\u767b\u5f55 MySQL\uff0c\u521b\u5efa testdb \u6570\u636e\u5e93\uff0c\u5e76\u5728\u6570\u636e\u5e93\u4e2d\u521b\u5efa\u4e00\u5f20\u6d4b\u8bd5\u8868 t1<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0create\u00a0database\u00a0if\u00a0not\u00a0exists\u00a0testdb;  \nQuery\u00a0OK,\u00a01\u00a0row\u00a0affected\u00a0(0.58\u00a0sec)  \nmysql&gt;\u00a0use\u00a0testdb;  \nDatabase\u00a0changed  \nmysql&gt;\u00a0create\u00a0table\u00a0if\u00a0not\u00a0exists\u00a0t1(i\u00a0int,\u00a0j\u00a0int);  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.05\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uff082\uff09\u5728\u5b57\u6bb5 i \u4e0a\u521b\u5efa\u7d22\u5f15\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0create\u00a0index\u00a0i_idx\u00a0on\u00a0t1(i);  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.34\u00a0sec)  \nRecords:\u00a00\u00a0\u00a0Duplicates:\u00a00\u00a0\u00a0Warnings:\u00a00  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uff083\uff09\u5728\u5b57\u6bb5 j \u4e0a\u521b\u5efa\u9690\u85cf\u7d22\u5f15\uff0c\u521b\u5efa\u9690\u85cf\u7d22\u5f15\u65f6\uff0c\u53ea\u9700\u8981\u5728\u521b\u5efa\u7d22\u5f15\u7684\u8bed\u53e5\u540e\u9762\u52a0\u4e0a invisible \u5173\u952e\u5b57\uff0c\u5982\u4e0b\u6240\u793a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0create\u00a0index\u00a0j_idx\u00a0on\u00a0t1(j)\u00a0invisible;  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.01\u00a0sec)  \nRecords:\u00a00\u00a0\u00a0Duplicates:\u00a00\u00a0\u00a0Warnings:\u00a00  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uff084\uff09\u67e5\u770b t1 \u8868\u4e2d\u7684\u7d22\u5f15\u60c5\u51b5\uff0c\u5982\u4e0b\u6240\u793a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0show\u00a0index\u00a0from\u00a0t1\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Table:\u00a0t1  \n\u00a0\u00a0\u00a0Non_unique:\u00a01  \n\u00a0\u00a0\u00a0\u00a0\u00a0Key_name:\u00a0i_idx  \n\u00a0Seq_in_index:\u00a01  \n\u00a0\u00a0Column_name:\u00a0i  \n\u00a0\u00a0\u00a0\u00a0Collation:\u00a0A  \n\u00a0\u00a0Cardinality:\u00a00  \n\u00a0\u00a0\u00a0\u00a0\u00a0Sub_part:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Packed:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Null:\u00a0YES  \n\u00a0\u00a0\u00a0Index_type:\u00a0BTREE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Comment:\u00a0  \nIndex_comment:\u00a0  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Visible:\u00a0YES  \n\u00a0\u00a0\u00a0Expression:\u00a0NULL  \n***************************\u00a02.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Table:\u00a0t1  \n\u00a0\u00a0\u00a0Non_unique:\u00a01  \n\u00a0\u00a0\u00a0\u00a0\u00a0Key_name:\u00a0j_idx  \n\u00a0Seq_in_index:\u00a01  \n\u00a0\u00a0Column_name:\u00a0j  \n\u00a0\u00a0\u00a0\u00a0Collation:\u00a0A  \n\u00a0\u00a0Cardinality:\u00a00  \n\u00a0\u00a0\u00a0\u00a0\u00a0Sub_part:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Packed:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Null:\u00a0YES  \n\u00a0\u00a0\u00a0Index_type:\u00a0BTREE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Comment:\u00a0  \nIndex_comment:\u00a0  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Visible:\u00a0NO  \n\u00a0\u00a0\u00a0Expression:\u00a0NULL  \n2\u00a0rows\u00a0in\u00a0set\u00a0(0.02\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230 t1 \u8868\u4e2d\u6709\u4e24\u4e2a\u7d22\u5f15\uff0c\u4e00\u4e2a\u662f i_idx\uff0c\u4e00\u4e2a\u662f j_idx\uff0ci_idx \u7684 Visible \u5c5e\u6027\u4e3a YES\uff0c\u8868\u793a\u8fd9\u4e2a\u7d22\u5f15\u53ef\u89c1\uff1b j_idx \u7684 Visibles \u5c5e\u6027\u4e3a NO\uff0c\u8868\u793a\u8fd9\u4e2a\u7d22\u5f15\u4e0d\u53ef\u89c1\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\uff085\uff09\u67e5\u770b\u67e5\u8be2\u4f18\u5316\u5668\u5bf9\u8fd9\u4e24\u4e2a\u7d22\u5f15\u7684\u4f7f\u7528\u60c5\u51b5\u3002 \u9996\u5148\uff0c\u4f7f\u7528\u5b57\u6bb5i\u8fdb\u884c\u67e5\u8be2\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0explain\u00a0select\u00a0*\u00a0from\u00a0t1\u00a0where\u00a0i\u00a0=\u00a01\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0id:\u00a01  \n\u00a0\u00a0select_type:\u00a0SIMPLE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0table:\u00a0t1  \n\u00a0\u00a0\u00a0partitions:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0type:\u00a0ref  \npossible_keys:\u00a0i_idx  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key:\u00a0i_idx  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key_len:\u00a05  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ref:\u00a0const  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0rows:\u00a01  \n\u00a0\u00a0\u00a0\u00a0\u00a0filtered:\u00a0100.00  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Extra:\u00a0NULL  \n1\u00a0row\u00a0in\u00a0set,\u00a01\u00a0warning\u00a0(0.02\u00a0sec)  \n\u53ef\u4ee5\u770b\u5230\uff0c\u67e5\u8be2\u4f18\u5316\u5668\u4f1a\u4f7f\u7528i\u5b57\u6bb5\u7684\u7d22\u5f15\u8fdb\u884c\u4f18\u5316\u3002  \n\u63a5\u4e0b\u6765\uff0c\u4f7f\u7528\u5b57\u6bb5j\u8fdb\u884c\u67e5\u8be2\uff0c\u5982\u4e0b\u6240\u793a\u3002  \nmysql&gt;\u00a0explain\u00a0select\u00a0*\u00a0from\u00a0t1\u00a0where\u00a0j\u00a0=\u00a01\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0id:\u00a01  \n\u00a0\u00a0select_type:\u00a0SIMPLE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0table:\u00a0t1  \n\u00a0\u00a0\u00a0partitions:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0type:\u00a0ALL  \npossible_keys:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key_len:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ref:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0rows:\u00a01  \n\u00a0\u00a0\u00a0\u00a0\u00a0filtered:\u00a0100.00  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Extra:\u00a0Using\u00a0where  \n1\u00a0row\u00a0in\u00a0set,\u00a01\u00a0warning\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u67e5\u8be2\u4f18\u5316\u5668\u5e76\u6ca1\u6709\u4f7f\u7528 j \u5b57\u6bb5\u4e0a\u7684\u9690\u85cf\u7d22\u5f15\uff0c\u4f1a\u4f7f\u7528\u5168\u8868\u626b\u63cf\u7684\u65b9\u5f0f\u67e5\u8be2\u6570\u636e\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\uff086\uff09\u4f7f\u9690\u85cf\u7d22\u5f15\u5bf9\u4f18\u5316\u5668\u53ef\u89c1\u5728 MySQL 8.x \u4e2d\u63d0\u4f9b\u4e86\u4e00\u79cd\u65b0\u7684\u6d4b\u8bd5\u65b9\u5f0f\uff0c\u53ef\u4ee5\u901a\u8fc7\u4f18\u5316\u5668\u7684\u4e00\u4e2a\u5f00\u5173\u6765\u6253\u5f00\u67d0\u4e2a\u8bbe\u7f6e\uff0c\u4f7f\u9690\u85cf\u7d22\u5f15\u5bf9\u67e5\u8be2\u4f18\u5316\u5668\u53ef\u89c1\u3002 \u67e5\u770b\u67e5\u8be2\u4f18\u5316\u5668\u7684\u5f00\u5173\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0select\u00a0@@optimizer_switch\u00a0\\G\u00a0  \n***************************\u00a01.\u00a0row\u00a0***************************  \n@@optimizer_switch:\u00a0index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,condition_fanout_filter=on,derived_merge=on,use_invisible_indexes=off,skip_scan=on,hash_join=on  \n1\u00a0row\u00a0in\u00a0set\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd9\u91cc\uff0c\u53ef\u4ee5\u770b\u5230\u5982\u4e0b\u4e00\u4e2a\u5c5e\u6027\u503c\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>use_invisible_indexes=off  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u8868\u793a\u4f18\u5316\u5668\u662f\u5426\u4f7f\u7528\u4e0d\u53ef\u89c1\u7d22\u5f15\uff0c\u9ed8\u8ba4\u4e3a off \u4e0d\u4f7f\u7528\u3002 \u63a5\u4e0b\u6765\uff0c\u5728 MySQL \u7684\u4f1a\u8bdd\u7ea7\u522b\u4f7f\u67e5\u8be2\u4f18\u5316\u5668\u4f7f\u7528\u4e0d\u53ef\u89c1\u7d22\u5f15\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0set\u00a0session\u00a0optimizer_switch=\"use_invisible_indexes=on\";  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u518d\u6b21\u67e5\u770b\u67e5\u8be2\u4f18\u5316\u5668\u7684\u5f00\u5173\u8bbe\u7f6e\uff0c\u5982\u4e0b\u6240\u793a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0select\u00a0@@optimizer_switch\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n@@optimizer_switch:\u00a0index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,condition_fanout_filter=on,derived_merge=on,use_invisible_indexes=on,skip_scan=on,hash_join=on  \n1\u00a0row\u00a0in\u00a0set\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u6b64\u65f6\uff0c\u53ef\u4ee5\u770b\u5230 use_invisible_indexes=on\uff0c\u8bf4\u660e\u9690\u85cf\u7d22\u5f15\u5bf9\u67e5\u8be2\u4f18\u5316\u5668\u53ef\u89c1\u4e86\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u518d\u6b21\u5206\u6790\u4f7f\u7528 t1 \u8868\u7684 j \u5b57\u6bb5\u67e5\u8be2\u6570\u636e\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0explain\u00a0select\u00a0*\u00a0from\u00a0t1\u00a0where\u00a0j\u00a0=\u00a01\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0id:\u00a01  \n\u00a0\u00a0select_type:\u00a0SIMPLE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0table:\u00a0t1  \n\u00a0\u00a0\u00a0partitions:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0type:\u00a0ref  \npossible_keys:\u00a0j_idx  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key:\u00a0j_idx  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key_len:\u00a05  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ref:\u00a0const  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0rows:\u00a01  \n\u00a0\u00a0\u00a0\u00a0\u00a0filtered:\u00a0100.00  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Extra:\u00a0NULL  \n1\u00a0row\u00a0in\u00a0set,\u00a01\u00a0warning\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u6b64\u65f6\u67e5\u8be2\u4f18\u5316\u5668\u4f7f\u7528j\u5b57\u6bb5\u4e0a\u7684\u9690\u85cf\u7d22\u5f15\u6765\u4f18\u5316\u67e5\u8be2\u4e86\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\uff087\uff09\u8bbe\u7f6e\u7d22\u5f15\u7684\u53ef\u89c1\u4e0e\u4e0d\u53ef\u89c1 \u5c06\u5b57\u6bb5 j \u4e0a\u7684\u9690\u85cf\u7d22\u5f15\u8bbe\u7f6e\u4e3a\u53ef\u89c1\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0alter\u00a0table\u00a0t1\u00a0alter\u00a0index\u00a0j_idx\u00a0visible;  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.01\u00a0sec)  \nRecords:\u00a00\u00a0\u00a0Duplicates:\u00a00\u00a0\u00a0Warnings:\u00a00  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5c06\u5b57\u6bb5 j \u4e0a\u7684\u7d22\u5f15\u8bbe\u7f6e\u4e3a\u4e0d\u53ef\u89c1\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0alter\u00a0table\u00a0t1\u00a0alter\u00a0index\u00a0j_idx\u00a0invisible;  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.01\u00a0sec)  \nRecords:\u00a00\u00a0\u00a0Duplicates:\u00a00\u00a0\u00a0Warnings:\u00a00  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uff088\uff09MySQL \u4e2d\u4e3b\u952e\u4e0d\u80fd\u8bbe\u7f6e\u4e3a\u4e0d\u53ef\u89c1\u7d22\u5f15 \u503c\u5f97\u6ce8\u610f\u7684\u662f\uff1a\u5728 MySQL \u4e2d\uff0c\u4e3b\u952e\u662f\u4e0d\u53ef\u4ee5\u8bbe\u7f6e\u4e3a\u4e0d\u53ef\u89c1\u7684\u3002 \u5728 testdb \u6570\u636e\u5e93\u4e2d\u521b\u5efa\u4e00\u5f20\u6d4b\u8bd5\u8868 t2\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0create\u00a0table\u00a0t2(i\u00a0int\u00a0not\u00a0null);  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.01\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u5728 t2 \u8868\u4e2d\u521b\u5efa\u4e00\u4e2a\u4e0d\u53ef\u89c1\u4e3b\u952e\uff0c\u5982\u4e0b\u6240\u793a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0alter\u00a0table\u00a0t2\u00a0add\u00a0primary\u00a0key\u00a0pk_t2(i)\u00a0invisible;\u00a0  \nERROR\u00a03522\u00a0(HY000):\u00a0A\u00a0primary\u00a0key\u00a0index\u00a0cannot\u00a0be\u00a0invisible  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u6b64\u65f6 SQL \u8bed\u53e5\u62a5\u9519\uff0c\u4e3b\u952e\u4e0d\u80fd\u88ab\u8bbe\u7f6e\u4e3a\u4e0d\u53ef\u89c1\u7d22\u5f15\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e8c\u3001\u964d\u5e8f\u7d22\u5f15<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1.\u964d\u5e8f\u7d22\u5f15\u6982\u8ff0<\/h3>\n\n\n\n<ul class=\"wp-block-list\"><li>MySQL 8.0 \u5f00\u59cb\u771f\u6b63\u652f\u6301\u964d\u5e8f\u7d22\u5f15\uff08descending index\uff09\u3002<\/li><li>\u53ea\u6709 InnoDB \u5b58\u50a8\u5f15\u64ce\u652f\u6301\u964d\u5e8f\u7d22\u5f15\uff0c\u53ea\u652f\u6301BTREE\u964d\u5e8f\u7d22\u5f15\u3002<\/li><li>MySQL 8.0 \u4e0d\u518d\u5bf9 GROUP BY \u64cd\u4f5c\u8fdb\u884c\u9690\u5f0f\u6392\u5e8f<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">2.\u964d\u5e8f\u7d22\u5f15\u64cd\u4f5c<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\uff081\uff09MySQL 5.7 \u4e2d\u652f\u6301\u7684\u8bed\u6cd5 \u9996\u5148\uff0c\u5728 MySQL 5.7 \u4e2d\u521b\u5efa\u6d4b\u8bd5\u6570\u636e\u5e93 testdb\uff0c\u5728\u6570\u636e\u5e93 testdb \u4e2d\u521b\u5efa\u6d4b\u8bd5\u8868 t2\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0create\u00a0database\u00a0if\u00a0not\u00a0exists\u00a0testdb;  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.71\u00a0sec)  \nmysql&gt;\u00a0use\u00a0testdb;  \nDatabase\u00a0changed  \nmysql&gt;\u00a0create\u00a0table\u00a0if\u00a0not\u00a0exists\u00a0t2(c1\u00a0int,\u00a0c2\u00a0int,\u00a0index\u00a0idx1(c1\u00a0asc,\u00a0c2\u00a0desc));  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.71\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5176\u4e2d\uff0c\u5728 t2 \u8868\u4e2d\u521b\u5efa\u4e86\u540d\u4e3a idx1 \u7684\u7d22\u5f15\uff0c\u7d22\u5f15\u4e2d c1 \u5b57\u6bb5\u5347\u5e8f\u6392\u5e8f\uff0cc2 \u5b57\u6bb5\u964d\u5e8f\u6392\u5e8f\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u67e5\u770b t2 \u8868\u7684\u521b\u5efa\u4fe1\u606f\uff0c\u5982\u4e0b\u6240\u793a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0show\u00a0create\u00a0table\u00a0t2\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Table:\u00a0t2  \nCreate\u00a0Table:\u00a0CREATE\u00a0TABLE\u00a0`t2`\u00a0(  \n\u00a0\u00a0`c1`\u00a0int(11)\u00a0DEFAULT\u00a0NULL,  \n\u00a0\u00a0`c2`\u00a0int(11)\u00a0DEFAULT\u00a0NULL,  \n\u00a0\u00a0KEY\u00a0`idx1`\u00a0(`c1`,`c2`)  \n)\u00a0ENGINE=InnoDB\u00a0DEFAULT\u00a0CHARSET=utf8mb4  \n1\u00a0row\u00a0in\u00a0set\u00a0(0.16\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0cMySQL 5.7 \u7248\u672c\u5728\u521b\u5efa\u8868\u7684\u4fe1\u606f\u4e2d\uff0c\u6ca1\u6709\u5b57\u6bb5 c1 \u548c c2 \u7684\u6392\u5e8f\u4fe1\u606f\uff0c\u9ed8\u8ba4\u90fd\u662f\u5347\u5e8f\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\uff082\uff09MySQL 8.0 \u4e2d\u652f\u6301\u7684\u8bed\u6cd5 \u5728 MySQL 8.x \u4e2d\u540c\u6837\u521b\u5efa t2 \u8868\uff0c\u5982\u4e0b\u6240\u793a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0create\u00a0table\u00a0if\u00a0not\u00a0exists\u00a0t2(c1\u00a0int,\u00a0c2\u00a0int,\u00a0index\u00a0idx1(c1\u00a0asc,\u00a0c2\u00a0desc));  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected,\u00a01\u00a0warning\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u67e5\u770b t2 \u8868\u7684\u521b\u5efa\u4fe1\u606f\uff0c\u5982\u4e0b\u6240\u793a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0show\u00a0create\u00a0table\u00a0t2\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Table:\u00a0t2  \nCreate\u00a0Table:\u00a0CREATE\u00a0TABLE\u00a0`t2`\u00a0(  \n\u00a0\u00a0`c1`\u00a0int(11)\u00a0DEFAULT\u00a0NULL,  \n\u00a0\u00a0`c2`\u00a0int(11)\u00a0DEFAULT\u00a0NULL,  \n\u00a0\u00a0KEY\u00a0`idx1`\u00a0(`c1`,`c2`\u00a0DESC)  \n)\u00a0ENGINE=InnoDB\u00a0DEFAULT\u00a0CHARSET=utf8mb4\u00a0COLLATE=utf8mb4_0900_ai_ci  \n1\u00a0row\u00a0in\u00a0set\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u5728 MySQL 8.x \u4e2d\uff0c\u521b\u5efa\u7684\u7d22\u5f15\u4e2d\u5b58\u5728\u5b57\u6bb5\u7684\u6392\u5e8f\u4fe1\u606f\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\uff083\uff09MySQL 5.7 \u4e2d\u67e5\u8be2\u4f18\u5316\u5668\u5bf9\u7d22\u5f15\u7684\u4f7f\u7528\u60c5\u51b5 \u9996\u5148\uff0c\u5728\u8868 t2 \u4e2d\u63d2\u5165\u4e00\u4e9b\u6570\u636e\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0insert\u00a0into\u00a0t2(c1,\u00a0c2)\u00a0values(1,\u00a0100),\u00a0(2,\u00a0200),\u00a0(3,\u00a0150),\u00a0(4,\u00a050);  \nQuery\u00a0OK,\u00a04\u00a0rows\u00a0affected\u00a0(0.19\u00a0sec)  \nRecords:\u00a04\u00a0\u00a0Duplicates:\u00a00\u00a0\u00a0Warnings:\u00a00  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u67e5\u8be2 t2 \u8868\u4e2d\u7684\u6570\u636e\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0select\u00a0*\u00a0from\u00a0t2;  \n+------+------+  \n|\u00a0c1\u00a0\u00a0\u00a0|\u00a0c2\u00a0\u00a0\u00a0|  \n+------+------+  \n|\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0100\u00a0|  \n|\u00a0\u00a0\u00a0\u00a02\u00a0|\u00a0\u00a0200\u00a0|  \n|\u00a0\u00a0\u00a0\u00a03\u00a0|\u00a0\u00a0150\u00a0|  \n|\u00a0\u00a0\u00a0\u00a04\u00a0|\u00a0\u00a0\u00a050\u00a0|  \n+------+------+  \n4\u00a0rows\u00a0in\u00a0set\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0ct2 \u8868\u4e2d\u7684\u6570\u636e\u63d2\u5165\u6210\u529f\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u67e5\u770b\u67e5\u8be2\u4f18\u5316\u5668\u5bf9\u7d22\u5f15\u7684\u4f7f\u7528\u60c5\u51b5\uff0c\u8fd9\u91cc\uff0c\u67e5\u8be2\u8bed\u53e5\u6309\u7167 c1 \u5b57\u6bb5\u5347\u5e8f\uff0c\u6309\u7167 c2 \u5b57\u6bb5\u964d\u5e8f\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0explain\u00a0select\u00a0*\u00a0from\u00a0t2\u00a0order\u00a0by\u00a0c1,\u00a0c2\u00a0desc\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0id:\u00a01  \n\u00a0\u00a0select_type:\u00a0SIMPLE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0table:\u00a0t2  \n\u00a0\u00a0\u00a0partitions:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0type:\u00a0index  \npossible_keys:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key:\u00a0idx1  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key_len:\u00a010  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ref:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0rows:\u00a04  \n\u00a0\u00a0\u00a0\u00a0\u00a0filtered:\u00a0100.00  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Extra:\u00a0Using\u00a0index;\u00a0Using\u00a0filesort  \n1\u00a0row\u00a0in\u00a0set,\u00a01\u00a0warning\u00a0(0.12\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u5728 MySQL 5.7 \u4e2d\uff0c\u6309\u7167 c2 \u5b57\u6bb5\u8fdb\u884c\u964d\u5e8f\u6392\u5e8f\uff0c\u5e76\u6ca1\u6709\u4f7f\u7528\u7d22\u5f15\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\uff084\uff09MySQL 8.x \u4e2d\u67e5\u8be2\u4f18\u5316\u5668\u5bf9\u964d\u5e8f\u7d22\u5f15\u7684\u4f7f\u7528\u60c5\u51b5\u3002 \u67e5\u770b\u67e5\u8be2\u4f18\u5316\u5668\u5bf9\u964d\u5e8f\u7d22\u5f15\u7684\u4f7f\u7528\u60c5\u51b5\u3002 \u9996\u5148\uff0c\u5728\u8868 t2 \u4e2d\u63d2\u5165\u4e00\u4e9b\u6570\u636e\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0insert\u00a0into\u00a0t2(c1,\u00a0c2)\u00a0values(1,\u00a0100),\u00a0(2,\u00a0200),\u00a0(3,\u00a0150),\u00a0(4,\u00a050);  \nQuery\u00a0OK,\u00a04\u00a0rows\u00a0affected\u00a0(0.00\u00a0sec)  \nRecords:\u00a04\u00a0\u00a0Duplicates:\u00a00\u00a0\u00a0Warnings:\u00a00  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u67e5\u8be2 t2 \u8868\u4e2d\u7684\u6570\u636e\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0select\u00a0*\u00a0from\u00a0t2;  \n+------+------+  \n|\u00a0c1\u00a0\u00a0\u00a0|\u00a0c2\u00a0\u00a0\u00a0|  \n+------+------+  \n|\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0100\u00a0|  \n|\u00a0\u00a0\u00a0\u00a02\u00a0|\u00a0\u00a0200\u00a0|  \n|\u00a0\u00a0\u00a0\u00a03\u00a0|\u00a0\u00a0150\u00a0|  \n|\u00a0\u00a0\u00a0\u00a04\u00a0|\u00a0\u00a0\u00a050\u00a0|  \n+------+------+  \n4\u00a0rows\u00a0in\u00a0set\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0ct2 \u8868\u4e2d\u7684\u6570\u636e\u63d2\u5165\u6210\u529f\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5728 MySQL \u4e2d\u5982\u679c\u521b\u5efa\u7684\u662f\u5347\u5e8f\u7d22\u5f15\uff0c\u5219\u6307\u5b9a\u67e5\u8be2\u7684\u65f6\u5019\uff0c\u53ea\u80fd\u6309\u7167\u5347\u5e8f\u7d22\u5f15\u7684\u65b9\u5f0f\u6307\u5b9a\u67e5\u8be2\uff0c\u8fd9\u6837\u624d\u80fd\u4f7f\u7528\u5347\u5e8f\u7d22\u5f15\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u67e5\u770b\u67e5\u8be2\u4f18\u5316\u5668\u5bf9\u7d22\u5f15\u7684\u4f7f\u7528\u60c5\u51b5\uff0c\u8fd9\u91cc\uff0c\u67e5\u8be2\u8bed\u53e5\u6309\u7167 c1 \u5b57\u6bb5\u5347\u5e8f\uff0c\u6309\u7167 c2 \u5b57\u6bb5\u964d\u5e8f\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0explain\u00a0select\u00a0*\u00a0from\u00a0t2\u00a0order\u00a0by\u00a0c1,\u00a0c2\u00a0desc\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0id:\u00a01  \n\u00a0\u00a0select_type:\u00a0SIMPLE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0table:\u00a0t2  \n\u00a0\u00a0\u00a0partitions:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0type:\u00a0index  \npossible_keys:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key:\u00a0idx1  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key_len:\u00a010  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ref:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0rows:\u00a04  \n\u00a0\u00a0\u00a0\u00a0\u00a0filtered:\u00a0100.00  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Extra:\u00a0Using\u00a0index  \n1\u00a0row\u00a0in\u00a0set,\u00a01\u00a0warning\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u5728 MySQL 8.x \u4e2d\uff0c\u6309\u7167 c2 \u5b57\u6bb5\u8fdb\u884c\u964d\u5e8f\u6392\u5e8f\uff0c\u4f7f\u7528\u4e86\u7d22\u5f15\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u4f7f\u7528 c1 \u5b57\u6bb5\u964d\u5e8f\uff0cc2 \u5b57\u6bb5\u5347\u5e8f\u6392\u5e8f\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0explain\u00a0select\u00a0*\u00a0from\u00a0t2\u00a0order\u00a0by\u00a0c1\u00a0desc,\u00a0c2\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0id:\u00a01  \n\u00a0\u00a0select_type:\u00a0SIMPLE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0table:\u00a0t2  \n\u00a0\u00a0\u00a0partitions:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0type:\u00a0index  \npossible_keys:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key:\u00a0idx1  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key_len:\u00a010  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ref:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0rows:\u00a04  \n\u00a0\u00a0\u00a0\u00a0\u00a0filtered:\u00a0100.00  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Extra:\u00a0Backward\u00a0index\u00a0scan;\u00a0Using\u00a0index  \n1\u00a0row\u00a0in\u00a0set,\u00a01\u00a0warning\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u5728 MySQL 8.x \u4e2d\u4ecd\u7136\u53ef\u4ee5\u4f7f\u7528\u7d22\u5f15\uff0c\u5e76\u4f7f\u7528\u4e86\u7d22\u5f15\u7684\u53cd\u5411\u626b\u63cf\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\uff085\uff09MySQL 8.x \u4e2d\u4e0d\u518d\u5bf9 GROUP BY \u8fdb\u884c\u9690\u5f0f\u6392\u5e8f<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5728 MySQL 5.7 \u4e2d\u6267\u884c\u5982\u4e0b\u547d\u4ee4\uff0c\u6309\u7167 c2 \u5b57\u6bb5\u8fdb\u884c\u5206\u7ec4\uff0c\u67e5\u8be2\u6bcf\u7ec4\u4e2d\u6570\u636e\u7684\u8bb0\u5f55\u6761\u6570\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0select\u00a0count(*),\u00a0c2\u00a0from\u00a0t2\u00a0group\u00a0by\u00a0c2;  \n+----------+------+  \n|\u00a0count(*)\u00a0|\u00a0c2\u00a0\u00a0\u00a0|  \n+----------+------+  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0\u00a050\u00a0|  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0100\u00a0|  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0150\u00a0|  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0200\u00a0|  \n+----------+------+  \n4\u00a0rows\u00a0in\u00a0set\u00a0(0.18\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u5728 MySQL 5.7 \u4e2d\uff0c\u5728 c2 \u5b57\u6bb5\u4e0a\u8fdb\u884c\u4e86\u6392\u5e8f\u64cd\u4f5c\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5728 MySQL 8.x \u4e2d\u6267\u884c\u5982\u4e0b\u547d\u4ee4\uff0c\u6309\u7167 c2 \u5b57\u6bb5\u8fdb\u884c\u5206\u7ec4\uff0c\u67e5\u8be2\u6bcf\u7ec4\u4e2d\u6570\u636e\u7684\u8bb0\u5f55\u6761\u6570\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0select\u00a0count(*),\u00a0c2\u00a0from\u00a0t2\u00a0group\u00a0by\u00a0c2;  \n+----------+------+  \n|\u00a0count(*)\u00a0|\u00a0c2\u00a0\u00a0\u00a0|  \n+----------+------+  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0100\u00a0|  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0200\u00a0|  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0150\u00a0|  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0\u00a050\u00a0|  \n+----------+------+  \n4\u00a0rows\u00a0in\u00a0set\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u5728 MySQL 8.x \u4e2d\uff0c\u5728 c2 \u5b57\u6bb5\u4e0a\u5e76\u6ca1\u6709\u8fdb\u884c\u6392\u5e8f\u64cd\u4f5c\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5728 MySQL 8.x \u4e2d\u5982\u679c\u9700\u8981\u5bf9 c2 \u5b57\u6bb5\u8fdb\u884c\u6392\u5e8f\uff0c\u5219\u9700\u8981\u4f7f\u7528 order by \u8bed\u53e5\u660e\u786e\u6307\u5b9a\u6392\u5e8f\u89c4\u5219\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0select\u00a0count(*),\u00a0c2\u00a0from\u00a0t2\u00a0group\u00a0by\u00a0c2\u00a0order\u00a0by\u00a0c2;  \n+----------+------+  \n|\u00a0count(*)\u00a0|\u00a0c2\u00a0\u00a0\u00a0|  \n+----------+------+  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0\u00a050\u00a0|  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0100\u00a0|  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0150\u00a0|  \n|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a01\u00a0|\u00a0\u00a0200\u00a0|  \n+----------+------+  \n4\u00a0rows\u00a0in\u00a0set\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">\u4e09\u3001\u51fd\u6570\u7d22\u5f15<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">1.\u51fd\u6570\u7d22\u5f15\u6982\u8ff0<\/h3>\n\n\n\n<ul class=\"wp-block-list\"><li>MySQL 8.0.13 \u5f00\u59cb\u652f\u6301\u5728\u7d22\u5f15\u4e2d\u4f7f\u7528\u51fd\u6570\uff08\u8868\u8fbe\u5f0f\uff09\u7684\u503c\u3002\n<\/li><li>\u652f\u6301\u964d\u5e8f\u7d22\u5f15\uff0c\u652f\u6301 JSON \u6570\u636e\u7684\u7d22\u5f15\n<\/li><li>\u51fd\u6570\u7d22\u5f15\u57fa\u4e8e\u865a\u62df\u5217\u529f\u80fd\u5b9e\u73b0\n<\/li><\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">2.\u51fd\u6570\u7d22\u5f15\u64cd\u4f5c<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\uff081\uff09\u521b\u5efa\u6d4b\u8bd5\u8868 t3 \u5728 testdb \u6570\u636e\u5e93\u4e2d\u521b\u5efa\u4e00\u5f20\u6d4b\u8bd5\u8868 t3\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0create\u00a0table\u00a0if\u00a0not\u00a0exists\u00a0t3(c1\u00a0varchar(10),\u00a0c2\u00a0varchar(10));  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.01\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uff082\uff09\u521b\u5efa\u666e\u901a\u7d22\u5f15\uff0c\u5728 c1 \u5b57\u6bb5\u4e0a\u521b\u5efa\u666e\u901a\u7d22\u5f15<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0create\u00a0index\u00a0idx1\u00a0on\u00a0t3(c1);  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.01\u00a0sec)  \nRecords:\u00a00\u00a0\u00a0Duplicates:\u00a00\u00a0\u00a0Warnings:\u00a00  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uff083\uff09\u521b\u5efa\u51fd\u6570\u7d22\u5f15 \u5728 c2 \u5b57\u6bb5\u4e0a\u521b\u5efa\u4e00\u4e2a\u5c06\u5b57\u6bb5\u503c\u8f6c\u5316\u4e3a\u5927\u5199\u7684\u51fd\u6570\u7d22\u5f15\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0create\u00a0index\u00a0func_index\u00a0on\u00a0t3\u00a0((UPPER(c2)));  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.02\u00a0sec)  \nRecords:\u00a00\u00a0\u00a0Duplicates:\u00a00\u00a0\u00a0Warnings:\u00a00  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uff084\uff09\u67e5\u770b t3 \u8868\u4e0a\u7684\u7d22\u5f15\u4fe1\u606f\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0show\u00a0index\u00a0from\u00a0t3\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Table:\u00a0t3  \n\u00a0\u00a0\u00a0Non_unique:\u00a01  \n\u00a0\u00a0\u00a0\u00a0\u00a0Key_name:\u00a0idx1  \n\u00a0Seq_in_index:\u00a01  \n\u00a0\u00a0Column_name:\u00a0c1  \n\u00a0\u00a0\u00a0\u00a0Collation:\u00a0A  \n\u00a0\u00a0Cardinality:\u00a00  \n\u00a0\u00a0\u00a0\u00a0\u00a0Sub_part:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Packed:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Null:\u00a0YES  \n\u00a0\u00a0\u00a0Index_type:\u00a0BTREE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Comment:\u00a0  \nIndex_comment:\u00a0  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Visible:\u00a0YES  \n\u00a0\u00a0\u00a0Expression:\u00a0NULL  \n***************************\u00a02.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Table:\u00a0t3  \n\u00a0\u00a0\u00a0Non_unique:\u00a01  \n\u00a0\u00a0\u00a0\u00a0\u00a0Key_name:\u00a0func_index  \n\u00a0Seq_in_index:\u00a01  \n\u00a0\u00a0Column_name:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0Collation:\u00a0A  \n\u00a0\u00a0Cardinality:\u00a00  \n\u00a0\u00a0\u00a0\u00a0\u00a0Sub_part:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Packed:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Null:\u00a0YES  \n\u00a0\u00a0\u00a0Index_type:\u00a0BTREE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Comment:\u00a0  \nIndex_comment:\u00a0  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Visible:\u00a0YES  \n\u00a0\u00a0\u00a0Expression:\u00a0upper(`c2`)  \n2\u00a0rows\u00a0in\u00a0set\u00a0(0.01\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uff085\uff09\u67e5\u770b\u67e5\u8be2\u4f18\u5316\u5668\u5bf9\u4e24\u4e2a\u7d22\u5f15\u7684\u4f7f\u7528\u60c5\u51b5\u3002\u9996\u5148\uff0c\u67e5\u770b c1 \u5b57\u6bb5\u7684\u5927\u5199\u503c\u662f\u5426\u7b49\u4e8e\u67d0\u4e2a\u7279\u5b9a\u7684\u503c\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0explain\u00a0select\u00a0*\u00a0from\u00a0t3\u00a0where\u00a0upper(c1)\u00a0=\u00a0'ABC'\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0id:\u00a01  \n\u00a0\u00a0select_type:\u00a0SIMPLE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0table:\u00a0t3  \n\u00a0\u00a0\u00a0partitions:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0type:\u00a0ALL  \npossible_keys:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key_len:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ref:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0rows:\u00a01  \n\u00a0\u00a0\u00a0\u00a0\u00a0filtered:\u00a0100.00  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Extra:\u00a0Using\u00a0where  \n1\u00a0row\u00a0in\u00a0set,\u00a01\u00a0warning\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u6ca1\u6709\u4f7f\u7528\u7d22\u5f15\uff0c\u8fdb\u884c\u4e86\u5168\u8868\u626b\u63cf\u64cd\u4f5c\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u67e5\u770b c2 \u5b57\u6bb5\u7684\u5927\u5199\u503c\u662f\u5426\u7b49\u4e8e\u67d0\u4e2a\u7279\u5b9a\u7684\u503c\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0explain\u00a0select\u00a0*\u00a0from\u00a0t3\u00a0where\u00a0upper(c2)\u00a0=\u00a0'ABC'\u00a0\\G\u00a0  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0id:\u00a01  \n\u00a0\u00a0select_type:\u00a0SIMPLE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0table:\u00a0t3  \n\u00a0\u00a0\u00a0partitions:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0type:\u00a0ref  \npossible_keys:\u00a0func_index  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key:\u00a0func_index  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key_len:\u00a043  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ref:\u00a0const  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0rows:\u00a01  \n\u00a0\u00a0\u00a0\u00a0\u00a0filtered:\u00a0100.00  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Extra:\u00a0NULL  \n1\u00a0row\u00a0in\u00a0set,\u00a01\u00a0warning\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u4f7f\u7528\u4e86\u51fd\u6570\u7d22\u5f15\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\uff086\uff09\u51fd\u6570\u7d22\u5f15\u5bf9 JSON \u6570\u636e\u7684\u7d22\u5f15 \u9996\u5148\uff0c\u521b\u5efa\u6d4b\u8bd5\u8868 emp\uff0c\u5e76\u5bf9 JSON \u6570\u636e\u8fdb\u884c\u7d22\u5f15\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0create\u00a0table\u00a0if\u00a0not\u00a0exists\u00a0emp(data\u00a0json,\u00a0index((CAST(data-&gt;&gt;'$.name'\u00a0as\u00a0char(30)))));  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.02\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u4e0a\u8ff0 SQL \u8bed\u53e5\u7684\u89e3\u91ca\u5982\u4e0b\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>JSON \u6570\u636e\u957f\u5ea6\u4e0d\u56fa\u5b9a\uff0c\u5982\u679c\u76f4\u63a5\u5bf9 JSON \u6570\u636e\u8fdb\u884c\u7d22\u5f15\uff0c\u53ef\u80fd\u4f1a\u8d85\u51fa\u7d22\u5f15\u957f\u5ea6\uff0c\u901a\u5e38\uff0c\u4f1a\u53ea\u622a\u53d6 JSON \u6570\u636e\u7684\u4e00\u90e8\u5206\u8fdb\u884c\u7d22\u5f15\u3002\n<\/li><li>CAST() \u7c7b\u578b\u8f6c\u6362\u51fd\u6570\uff0c\u628a\u6570\u636e\u8f6c\u5316\u4e3a char(30) \u7c7b\u578b\u3002\u4f7f\u7528\u65b9\u5f0f\u4e3a CAST(\u6570\u636e as \u6570\u636e\u7c7b\u578b)\u3002\n<\/li><li>data -&gt;&gt; &#8216;$.name&#8217; \u8868\u793a JSON \u7684\u8fd0\u7b97\u7b26\n<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u7b80\u5355\u7684\u7406\u89e3\u4e3a\uff0c\u5c31\u662f\u53d6 name \u8282\u70b9\u7684\u503c\uff0c\u5c06\u5176\u8f6c\u5316\u4e3a char(30) \u7c7b\u578b\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u67e5\u770b emp \u8868\u4e2d\u7684\u7d22\u5f15\u60c5\u51b5\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0show\u00a0index\u00a0from\u00a0emp\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Table:\u00a0emp  \n\u00a0\u00a0\u00a0Non_unique:\u00a01  \n\u00a0\u00a0\u00a0\u00a0\u00a0Key_name:\u00a0functional_index  \n\u00a0Seq_in_index:\u00a01  \n\u00a0\u00a0Column_name:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0Collation:\u00a0A  \n\u00a0\u00a0Cardinality:\u00a00  \n\u00a0\u00a0\u00a0\u00a0\u00a0Sub_part:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Packed:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Null:\u00a0YES  \n\u00a0\u00a0\u00a0Index_type:\u00a0BTREE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Comment:\u00a0  \nIndex_comment:\u00a0  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Visible:\u00a0YES  \n\u00a0\u00a0\u00a0Expression:\u00a0cast(json_unquote(json_extract(`data`,_utf8mb4\\'$.name\\'))\u00a0as\u00a0char(30)\u00a0charset\u00a0utf8mb4)  \n1\u00a0row\u00a0in\u00a0set\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\uff087\uff09\u51fd\u6570\u7d22\u5f15\u57fa\u4e8e\u865a\u62df\u5217\u5b9e\u73b0 \u9996\u5148\uff0c\u67e5\u770b t3 \u8868\u7684\u4fe1\u606f\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0desc\u00a0t3;  \n+-------+-------------+------+-----+---------+-------+  \n|\u00a0Field\u00a0|\u00a0Type\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0|\u00a0Null\u00a0|\u00a0Key\u00a0|\u00a0Default\u00a0|\u00a0Extra\u00a0|  \n+-------+-------------+------+-----+---------+-------+  \n|\u00a0c1\u00a0\u00a0\u00a0\u00a0|\u00a0varchar(10)\u00a0|\u00a0YES\u00a0\u00a0|\u00a0MUL\u00a0|\u00a0NULL\u00a0\u00a0\u00a0\u00a0|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0|  \n|\u00a0c2\u00a0\u00a0\u00a0\u00a0|\u00a0varchar(10)\u00a0|\u00a0YES\u00a0\u00a0|\u00a0\u00a0\u00a0\u00a0\u00a0|\u00a0NULL\u00a0\u00a0\u00a0\u00a0|\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0|  \n+-------+-------------+------+-----+---------+-------+  \n2\u00a0rows\u00a0in\u00a0set\u00a0(0.00\u00a0sec)  \n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u5728 c1 \u4e0a\u5efa\u7acb\u4e86\u666e\u901a\u7d22\u5f15\uff0c\u5728 c2 \u4e0a\u5efa\u7acb\u4e86\u51fd\u6570\u7d22\u5f15\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u5728 t3 \u8868\u4e2d\u6dfb\u52a0\u4e00\u5217 c3\uff0c\u6a21\u62df c2 \u4e0a\u7684\u51fd\u6570\u7d22\u5f15\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0alter\u00a0table\u00a0t3\u00a0add\u00a0column\u00a0c3\u00a0varchar(10)\u00a0generated\u00a0always\u00a0as\u00a0(upper(c1));  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.03\u00a0sec)  \nRecords:\u00a00\u00a0\u00a0Duplicates:\u00a00\u00a0\u00a0Warnings:\u00a00  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">c3 \u5217\u662f\u4e00\u4e2a\u8ba1\u7b97\u5217\uff0cc3 \u5b57\u6bb5\u7684\u503c\u603b\u662f\u4f7f\u7528 c1 \u5b57\u6bb5\u8f6c\u5316\u4e3a\u5927\u5199\u7684\u7ed3\u679c\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u5411 t3 \u8868\u4e2d\u63d2\u5165\u4e00\u6761\u6570\u636e\uff0c\u5176\u4e2d\uff0cc3 \u5217\u662f\u4e00\u4e2a\u8ba1\u7b97\u5217\uff0cc3 \u5b57\u6bb5\u7684\u503c\u603b\u662f\u4f7f\u7528 c1 \u5b57\u6bb5\u8f6c\u5316\u4e3a\u5927\u5199\u7684\u7ed3\u679c\uff0c\u5728\u63d2\u5165\u6570\u636e\u7684\u65f6\u5019\uff0c\u4e0d\u9700\u8981\u4e3a c3 \u5217\u63d2\u5165\u6570\u636e\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0insert\u00a0into\u00a0t3(c1,\u00a0c2)\u00a0values\u00a0('abc',\u00a0'def');  \nQuery\u00a0OK,\u00a01\u00a0row\u00a0affected\u00a0(0.00\u00a0sec)  \n<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u67e5\u8be2 t3 \u8868\u4e2d\u7684\u6570\u636e\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0select\u00a0*\u00a0from\u00a0t3;  \n+------+------+------+  \n|\u00a0c1\u00a0\u00a0\u00a0|\u00a0c2\u00a0\u00a0\u00a0|\u00a0c3\u00a0\u00a0\u00a0|  \n+------+------+------+  \n|\u00a0abc\u00a0\u00a0|\u00a0def\u00a0\u00a0|\u00a0ABC\u00a0\u00a0|  \n+------+------+------+  \n1\u00a0row\u00a0in\u00a0set\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u53ef\u4ee5\u770b\u5230\uff0c\u5e76\u4e0d\u9700\u8981\u5411 c3 \u5217\u4e2d\u63d2\u5165\u6570\u636e\uff0cc3 \u5217\u7684\u6570\u636e\u4e3a c1 \u5b57\u6bb5\u7684\u5927\u5199\u7ed3\u679c\u6570\u636e\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\u5982\u679c\u60f3\u6a21\u62df\u51fd\u6570\u7d22\u5f15\u7684\u6548\u679c\uff0c\u5219\u53ef\u4ee5\u4f7f\u7528\u5982\u4e0b\u65b9\u5f0f\u3002\u9996\u5148\uff0c\u5728 c3 \u5217\u4e0a\u6dfb\u52a0\u7d22\u5f15\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0create\u00a0index\u00a0idx3\u00a0on\u00a0t3(c3);  \nQuery\u00a0OK,\u00a00\u00a0rows\u00a0affected\u00a0(0.11\u00a0sec)  \nRecords:\u00a00\u00a0\u00a0Duplicates:\u00a00\u00a0\u00a0Warnings:\u00a00  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u63a5\u4e0b\u6765\uff0c\u518d\u6b21\u67e5\u770b c1 \u5b57\u6bb5\u7684\u5927\u5199\u503c\u662f\u5426\u7b49\u4e8e\u67d0\u4e2a\u7279\u5b9a\u7684\u503c\uff0c\u5982\u4e0b\u6240\u793a\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>mysql&gt;\u00a0explain\u00a0select\u00a0*\u00a0from\u00a0t3\u00a0where\u00a0upper(c1)\u00a0=\u00a0'ABC'\u00a0\\G  \n***************************\u00a01.\u00a0row\u00a0***************************  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0id:\u00a01  \n\u00a0\u00a0select_type:\u00a0SIMPLE  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0table:\u00a0t3  \n\u00a0\u00a0\u00a0partitions:\u00a0NULL  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0type:\u00a0ref  \npossible_keys:\u00a0idx3  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key:\u00a0idx3  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0key_len:\u00a043  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0ref:\u00a0const  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0rows:\u00a01  \n\u00a0\u00a0\u00a0\u00a0\u00a0filtered:\u00a0100.00  \n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Extra:\u00a0NULL  \n1\u00a0row\u00a0in\u00a0set,\u00a01\u00a0warning\u00a0(0.00\u00a0sec)  <\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u6b64\u65f6\uff0c\u5c31\u4f7f\u7528\u4e86 idx3 \u7d22\u5f15\u3002<\/p>\n<!-- <audio autoplay=\"autoplay\" height=\"100\" width=\"100\" hidden=\"true\"><source src=\"https:\/\/c.coka.la\/orAvPR.mp3\" type=\"audio\/mp3\"\/><\/audio><img decoding=\"async\" src=\"https:\/\/images.weserv.nl\/?url=https:\/\/ws3.sinaimg.cn\/large\/8fa5dcfcgy1g4em3rzar5j20ib089ae0.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/> --><p><!-- <img decoding=\"async\" src=\"https:\/\/raw.githubusercontent.com\/xmt1139057136\/xttblog\/master\/8fa5dcfcgy1g4em3rzar5j20ib089ae0.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/>--><img decoding=\"async\" src=\"https:\/\/saas.51autoparts.cn\/api\/admin\/sys-file\/oss\/file?fileName=84db51f8561e448f9a4fda2eff0811f9.jpg\" alt=\"\u4e1a\u4f59\u8349\u516c\u4f17\u53f7\"\/><\/p><p>\u6700\u540e\uff0c\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u4e2a\u4eba\u5fae\u4fe1\u516c\u4f17\u53f7\uff1a\u4e1a\u4f59\u8349\uff08yyucao\uff09\uff01<b>\u53ef\u52a0\u4f5c\u8005\u5fae\u4fe1\u53f7\uff1a<font color=\"red\">xttblog2<\/font>\u3002\u5907\u6ce8\uff1a\u201c1\u201d\uff0c\u6dfb\u52a0\u535a\u4e3b\u5fae\u4fe1\u62c9\u4f60\u8fdb\u5fae\u4fe1\u7fa4\u3002\u5907\u6ce8\u9519\u8bef\u4e0d\u4f1a\u540c\u610f\u597d\u53cb\u7533\u8bf7\u3002<\/b>\u518d\u6b21\u611f\u8c22\u60a8\u7684\u5173\u6ce8\uff01\u540e\u7eed\u6709\u7cbe\u5f69\u5185\u5bb9\u4f1a\u7b2c\u4e00\u65f6\u95f4\u53d1\u7ed9\u60a8\uff01\u539f\u521b\u6587\u7ae0\u6295\u7a3f\u8bf7\u53d1\u9001\u81f3532009913@qq.com\u90ae\u7bb1\u3002\u5546\u52a1\u5408\u4f5c\u4e5f\u53ef\u6dfb\u52a0\u4f5c\u8005\u5fae\u4fe1\u8fdb\u884c\u8054\u7cfb\uff01<\/p><p>\u672c\u6587\u539f\u6587\u51fa\u5904\uff1a<a href=\"https:\/\/www.xttblog.com\">\u4e1a\u4f59\u8349<\/a>\uff1a &raquo; <a href=\"https:\/\/www.xttblog.com\/?p=5257\">MySQL8\u4e2d\u65b0\u589e\u4e86\u4e09\u5927\u7d22\u5f15\uff0c\u9690\u85cf\u7d22\u5f15\u3001\u964d\u5e8f\u7d22\u5f15\u3001\u51fd\u6570\u7d22\u5f15<\/a><\/p><!-- <div class=\"bd-reward-stl\"><button id=\"bdRewardBtn\"><span><\/span><\/button><\/div> -->","protected":false},"excerpt":{"rendered":"<p>\u4eca\u5929\u6211\u4eec\u4e00\u8d77\u6765\u804a\u804a MySQL 8.x \u7248\u672c\u4e2d\u65b0\u589e\u7684\u4e09\u5927\u7d22\u5f15\u3002MySQL 8.x \u4e2d\u65b0\u589e\u4e86\u4e09\u79cd\u7d22\u5f15\u65b9\u5f0f\uff0c\u5982\u4e0b\u6240 [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12],"tags":[83,580,392,391,393],"class_list":["post-5257","post","type-post","status-publish","format-standard","hentry","category-sql","tag-mysql","tag-mysql----dba"],"_links":{"self":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/5257","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=5257"}],"version-history":[{"count":1,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/5257\/revisions"}],"predecessor-version":[{"id":5258,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/5257\/revisions\/5258"}],"wp:attachment":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5257"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5257"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5257"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}