{"id":5123,"date":"2020-11-17T10:36:19","date_gmt":"2020-11-17T02:36:19","guid":{"rendered":"https:\/\/www.xttblog.com\/?p=5123"},"modified":"2020-11-17T10:36:19","modified_gmt":"2020-11-17T02:36:19","slug":"mysql-%e7%9a%84-21-%e4%b8%aa%e8%a7%84%e8%8c%83%e3%80%81%e4%bc%98%e5%8c%96%e6%9c%80%e4%bd%b3%e5%ae%9e%e8%b7%b5%ef%bc%81","status":"publish","type":"post","link":"https:\/\/www.xttblog.com\/?p=5123","title":{"rendered":"MySQL \u7684 21 \u4e2a\u89c4\u8303\u3001\u4f18\u5316\u6700\u4f73\u5b9e\u8df5\uff01"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">\u524d\u8a00<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u6bcf\u4e00\u4e2a\u597d\u4e60\u60ef\u90fd\u662f\u4e00\u7b14\u8d22\u5bcc\uff0c\u672c\u6587\u5206 SQL \u540e\u6094\u836f\uff0cSQL \u6027\u80fd\u4f18\u5316\uff0cSQL \u89c4\u8303\u4f18\u96c5\u4e09\u4e2a\u65b9\u5411\uff0c\u5206\u4eab\u5199 SQL \u7684 21 \u4e2a\u597d\u4e60\u60ef\u548c\u6700\u4f73\u5b9e\u8df5\uff01<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u5199\u5b8cSQL\u5148explain\u67e5\u770b\u6267\u884c\u8ba1\u5212\uff08SQL\u6027\u80fd\u4f18\u5316\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u65e5\u5e38\u5f00\u53d1\u5199 SQL \u7684\u65f6\u5019\uff0c\u5c3d\u91cf\u517b\u6210\u8fd9\u4e2a\u597d\u4e60\u60ef\u5440\uff1a\u5199\u5b8c SQL \u540e\uff0c\u7528 explain \u5206\u6790\u4e00\u4e0b\uff0c\u5c24\u5176\u6ce8\u610f\u8d70\u4e0d\u8d70\u7d22\u5f15\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>explain\u00a0select\u00a0*\u00a0from\u00a0user\u00a0where\u00a0userid\u00a0=\u00a010086\u00a0or\u00a0age\u00a0=18;<\/code><\/pre>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/2020\/sql1.png\" alt=\"\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">\u64cd\u4f5c delete \u6216\u8005 update \u8bed\u53e5\uff0c\u52a0\u4e2a limit(SQL\u540e\u6094\u836f\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u5728\u6267\u884c\u5220\u9664\u6216\u8005\u66f4\u65b0\u8bed\u53e5\uff0c\u5c3d\u91cf\u52a0\u4e0a limit\uff0c\u4ee5\u4e0b\u9762\u7684\u8fd9\u6761 SQL \u4e3a\u4f8b\u5427\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>delete\u00a0from\u00a0euser\u00a0where\u00a0age\u00a0&gt;\u00a030\u00a0limit\u00a0200;<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u56e0\u4e3a\u52a0\u4e86 limit \u4e3b\u8981\u6709\u8fd9\u4e9b\u597d\u5904\uff1a<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/2020\/sql2.png\" alt=\"\" \/><\/figure>\n\n\n\n<ul class=\"wp-block-list\"><li>\u964d\u4f4e\u5199\u9519 SQL \u7684\u4ee3\u4ef7\uff0c\u4f60\u5728\u547d\u4ee4\u884c\u6267\u884c\u8fd9\u4e2a SQL \u7684\u65f6\u5019\uff0c\u5982\u679c\u4e0d\u52a0 limit\uff0c\u6267\u884c\u7684\u65f6\u5019\u4e00\u4e2a\u4e0d\u5c0f\u5fc3\u624b\u6296\uff0c\u53ef\u80fd\u6570\u636e\u5168\u5220\u6389\u4e86\uff0c\u5982\u679c\u5220\u9519\u4e86\u5462\uff1f\u52a0\u4e86 limit 200\uff0c\u5c31\u4e0d\u4e00\u6837\u4e86\u3002\u5220\u9519\u4e5f\u53ea\u662f\u4e22\u5931 200 \u6761\u6570\u636e\uff0c\u53ef\u4ee5\u901a\u8fc7 binlog \u65e5\u5fd7\u5feb\u901f\u6062\u590d\u7684\u3002<\/li><li>SQL \u6548\u7387\u5f88\u53ef\u80fd\u66f4\u9ad8\uff0c\u4f60\u5728 SQL \u884c\u4e2d\uff0c\u52a0\u4e86 limit 1\uff0c\u5982\u679c\u7b2c\u4e00\u6761\u5c31\u547d\u4e2d\u76ee\u6807 return\uff0c \u6ca1\u6709 limit \u7684\u8bdd\uff0c\u8fd8\u4f1a\u7ee7\u7eed\u6267\u884c\u626b\u63cf\u8868\u3002<\/li><li>\u907f\u514d\u4e86\u957f\u4e8b\u52a1\uff0cdelete \u6267\u884c\u65f6\uff0c\u5982\u679c age \u52a0\u4e86\u7d22\u5f15\uff0cMySQL\u4f1a\u5c06\u6240\u6709\u76f8\u5173\u7684\u884c\u52a0\u5199\u9501\u548c\u95f4\u9699\u9501\uff0c\u6240\u6709\u6267\u884c\u76f8\u5173\u884c\u4f1a\u88ab\u9501\u4f4f\uff0c\u5982\u679c\u5220\u9664\u6570\u91cf\u5927\uff0c\u4f1a\u76f4\u63a5\u5f71\u54cd\u76f8\u5173\u4e1a\u52a1\u65e0\u6cd5\u4f7f\u7528\u3002<\/li><li>\u6570\u636e\u91cf\u5927\u7684\u8bdd\uff0c\u5bb9\u6613\u628a CPU \u6253\u6ee1\uff0c\u5982\u679c\u4f60\u5220\u9664\u6570\u636e\u91cf\u5f88\u5927\u65f6\uff0c\u4e0d\u52a0 limit \u9650\u5236\u4e00\u4e0b\u8bb0\u5f55\u6570\uff0c\u5bb9\u6613\u628a cpu \u6253\u6ee1\uff0c\u5bfc\u81f4\u8d8a\u5220\u8d8a\u6162\u7684\u3002<\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">\u8bbe\u8ba1\u8868\u7684\u65f6\u5019\uff0c\u6240\u6709\u8868\u548c\u5b57\u6bb5\u90fd\u6dfb\u52a0\u76f8\u5e94\u7684\u6ce8\u91ca\uff08SQL\u89c4\u8303\u4f18\u96c5\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd9\u4e2a\u597d\u4e60\u60ef\u4e00\u5b9a\u8981\u517b\u6210\u5566\uff0c\u8bbe\u8ba1\u6570\u636e\u5e93\u8868\u7684\u65f6\u5019\uff0c\u6240\u6709\u8868\u548c\u5b57\u6bb5\u90fd\u6dfb\u52a0\u76f8\u5e94\u7684\u6ce8\u91ca\uff0c\u540e\u9762\u66f4\u5bb9\u6613\u7ef4\u62a4\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u6b63\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>CREATE TABLE `account` (\n  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '\u4e3b\u952eId',\n  `name` varchar(255) DEFAULT NULL COMMENT '\u8d26\u6237\u540d',\n  `balance` int(11) DEFAULT NULL COMMENT '\u4f59\u989d',\n  `create_time` datetime NOT NULL COMMENT '\u521b\u5efa\u65f6\u95f4',\n  `update_time` datetime NOT NULL ON UPDATE CURRENT_TIMESTAMP COMMENT '\u66f4\u65b0\u65f6\u95f4',\n  PRIMARY KEY (`id`),\n  KEY `idx_name` (`name`) USING BTREE\n) ENGINE=InnoDB AUTO_INCREMENT=1570068 DEFAULT CHARSET=utf8 ROW_FORMAT=REDUNDANT COMMENT='\u8d26\u6237\u8868';<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u53cd\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>CREATE TABLE `account` (\n  `id` int(11) NOT NULL AUTO_INCREMENT,\n  `name` varchar(255) DEFAULT NULL,\n  `balance` int(11) DEFAULT NULL,\n  `create_time` datetime NOT NULL ,\n  `update_time` datetime NOT NULL ON UPDATE CURRENT_TIMESTAMP,\n  PRIMARY KEY (`id`),\n  KEY `idx_name` (`name`) USING BTREE\n) ENGINE=InnoDB AUTO_INCREMENT=1570068 DEFAULT CHARSET=utf8;<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">SQL\u4e66\u5199\u683c\u5f0f\uff0c\u5173\u952e\u5b57\u5927\u5c0f\u4fdd\u6301\u4e00\u81f4\uff0c\u4f7f\u7528\u7f29\u8fdb\u3002\uff08SQL\u89c4\u8303\u4f18\u96c5\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u6b63\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT\u00a0stu.name,\u00a0sum(stu.score)FROM\u00a0Student\u00a0stuWHERE\u00a0stu.classNo\u00a0=\u00a0'1\u73ed'GROUP\u00a0BY\u00a0stu.name<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u53cd\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>SELECT\u00a0stu.name,\u00a0sum(stu.score)\u00a0from\u00a0Student\u00a0stu\u00a0WHERE\u00a0stu.classNo\u00a0=\u00a0'1\u73ed'\u00a0group\u00a0by\u00a0stu.name.<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\">\u663e\u7136\uff0c\u7edf\u4e00\u5173\u952e\u5b57\u5927\u5c0f\u5199\u4e00\u81f4\uff0c\u4f7f\u7528\u7f29\u8fdb\u5bf9\u9f50\uff0c\u4f1a\u4f7f\u4f60\u7684 SQL \u770b\u8d77\u6765\u66f4\u4f18\u96c5~<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">INSERT\u8bed\u53e5\u6807\u660e\u5bf9\u5e94\u7684\u5b57\u6bb5\u540d\u79f0\uff08SQL\u89c4\u8303\u4f18\u96c5\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u53cd\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>insert\u00a0into\u00a0Student\u00a0values\u00a0('666','\u4e1a\u4f59\u8349','100');<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u6b63\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>insert\u00a0into\u00a0Student(student_id,name,score)\u00a0values\u00a0('666','\u4e1a\u4f59\u8349','100');<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">\u53d8\u66f4SQL\u64cd\u4f5c\u5148\u5728\u6d4b\u8bd5\u73af\u5883\u6267\u884c\uff0c\u5199\u660e\u8be6\u7ec6\u7684\u64cd\u4f5c\u6b65\u9aa4\u4ee5\u53ca\u56de\u6eda\u65b9\u6848\uff0c\u5e76\u5728\u4e0a\u751f\u4ea7\u524dreview\u3002\uff08SQL\u540e\u6094\u836f\uff09<\/h2>\n\n\n\n<ul class=\"wp-block-list\"><li>\u53d8\u66f4 SQL \u64cd\u4f5c\u5148\u5728\u6d4b\u8bd5\u73af\u5883\u6d4b\u8bd5\uff0c\u907f\u514d\u6709\u8bed\u6cd5\u9519\u8bef\u5c31\u653e\u5230\u751f\u4ea7\u4e0a\u4e86\u3002<\/li><li>\u53d8\u66f4 Sql \u64cd\u4f5c\u9700\u8981\u5199\u660e\u8be6\u7ec6\u64cd\u4f5c\u6b65\u9aa4\uff0c\u5c24\u5176\u6709\u4f9d\u8d56\u5173\u7cfb\u7684\u65f6\u5019\uff0c\u5982\uff1a\u5148\u4fee\u6539\u8868\u7ed3\u6784\u518d\u8865\u5145\u5bf9\u5e94\u7684\u6570\u636e\u3002<\/li><li>\u53d8\u66f4 Sql \u64cd\u4f5c\u6709\u56de\u6eda\u65b9\u6848\uff0c\u5e76\u5728\u4e0a\u751f\u4ea7\u524d\uff0creview \u5bf9\u5e94\u53d8\u66f4 SQL\u3002<\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">\u8bbe\u8ba1\u6570\u636e\u5e93\u8868\u7684\u65f6\u5019\uff0c\u52a0\u4e0a\u4e09\u4e2a\u5b57\u6bb5\uff1a\u4e3b\u952e\uff0ccreate_time\uff0cupdate_time\u3002\uff08SQL \u89c4\u8303\u4f18\u96c5\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u53cd\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>CREATE TABLE `account` (\n  `name` varchar(255) DEFAULT NULL COMMENT '\u8d26\u6237\u540d',\n  `balance` int(11) DEFAULT NULL COMMENT '\u4f59\u989d',\n) ENGINE=InnoDB AUTO_INCREMENT=1570068 DEFAULT CHARSET=utf8 ROW_FORMAT=REDUNDANT COMMENT='\u8d26\u6237\u8868';<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u6b63\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>CREATE TABLE `account` (\n  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '\u4e3b\u952eId',\n  `name` varchar(255) DEFAULT NULL COMMENT '\u8d26\u6237\u540d',\n  `balance` int(11) DEFAULT NULL COMMENT '\u4f59\u989d',\n  `create_time` datetime NOT NULL COMMENT '\u521b\u5efa\u65f6\u95f4',\n  `update_time` datetime NOT NULL ON UPDATE CURRENT_TIMESTAMP COMMENT '\u66f4\u65b0\u65f6\u95f4',\n  PRIMARY KEY (`id`),\n  KEY `idx_name` (`name`) USING BTREE\n) ENGINE=InnoDB AUTO_INCREMENT=1570068 DEFAULT CHARSET=utf8 ROW_FORMAT=REDUNDANT COMMENT='\u8d26\u6237\u8868';<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u7406\u7531\uff1a<\/code><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u4e3b\u952e\u4e00\u5b9a\u8981\u52a0\u4e0a\u7684\uff0c\u6ca1\u6709\u4e3b\u952e\u7684\u8868\u662f\u6ca1\u6709\u7075\u9b42\u7684<\/li><li>\u521b\u5efa\u65f6\u95f4\u548c\u66f4\u65b0\u65f6\u95f4\u7684\u8bdd\uff0c\u8fd8\u662f\u5efa\u8bae\u52a0\u4e0a\u5427\uff0c\u8be6\u7ec6\u5ba1\u8ba1\u3001\u8ddf\u8e2a\u8bb0\u5f55\uff0c\u90fd\u662f\u6709\u7528\u7684\u3002<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u963f\u91cc\u5f00\u53d1\u624b\u518c\u4e5f\u63d0\u5230\u8fd9\u4e2a\u70b9\uff0c\u5982\u56fe<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/2020\/sql3.png\" alt=\"\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">\u5199\u5b8c SQL \u8bed\u53e5\uff0c\u68c0\u67e5 where,order by,group by\u540e\u9762\u7684\u5217\uff0c\u591a\u8868\u5173\u8054\u7684\u5217\u662f\u5426\u5df2\u52a0\u7d22\u5f15\uff0c\u4f18\u5148\u8003\u8651\u7ec4\u5408\u7d22\u5f15\u3002\uff08SQL\u6027\u80fd\u4f18\u5316\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u53cd\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>select\u00a0*\u00a0from\u00a0user\u00a0where\u00a0address\u00a0='\u6df1\u5733'\u00a0order\u00a0by\u00a0age\u00a0;<\/code><\/pre>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/2020\/sql4.png\" alt=\"\" \/><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u6b63\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>--\u00a0\u6dfb\u52a0\u7d22\u5f15alter\u00a0table\u00a0user\u00a0add\u00a0index\u00a0idx_address_age\u00a0(address,age)<\/code><\/pre>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/2020\/sql5.png\" alt=\"\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">\u4fee\u6539\u6216\u5220\u9664\u91cd\u8981\u6570\u636e\u524d\uff0c\u8981\u5148\u5907\u4efd\uff0c\u5148\u5907\u4efd\uff0c\u5148\u5907\u4efd\uff08SQL \u540e\u6094\u836f\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u5982\u679c\u8981\u4fee\u6539\u6216\u5220\u9664\u6570\u636e\uff0c\u5728\u6267\u884cSQL\u524d\u4e00\u5b9a\u8981\u5148\u5907\u4efd\u8981\u4fee\u6539\u7684\u6570\u636e\uff0c\u4e07\u4e00\u8bef\u64cd\u4f5c\uff0c\u8fd8\u80fd\u5403\u53e3\u540e\u6094\u836f\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">where\u540e\u9762\u7684\u5b57\u6bb5\uff0c\u7559\u610f\u5176\u6570\u636e\u7c7b\u578b\u7684\u9690\u5f0f\u8f6c\u6362\uff08SQL \u6027\u80fd\u4f18\u5316\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u53cd\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>\/\/userid\u00a0\u662fvarchar\u5b57\u7b26\u4e32\u7c7b\u578bselect\u00a0*\u00a0from\u00a0user\u00a0where\u00a0userid\u00a0=123;<\/code><\/pre>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/2020\/sql6.png\" alt=\"\" \/><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">\n<code>\u6b63\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>select\u00a0*\u00a0from\u00a0user\u00a0where\u00a0userid\u00a0='123';<\/code><\/pre>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/2020\/sql7.png\" alt=\"\" \/><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u7406\u7531\uff1a<\/code><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u56e0\u4e3a\u4e0d\u52a0\u5355\u5f15\u53f7\u65f6\uff0c\u662f\u5b57\u7b26\u4e32\u8ddf\u6570\u5b57\u7684\u6bd4\u8f83\uff0c\u5b83\u4eec\u7c7b\u578b\u4e0d\u5339\u914d\uff0cMySQL \u4f1a\u505a\u9690\u5f0f\u7684\u7c7b\u578b\u8f6c\u6362\uff0c\u628a\u5b83\u4eec\u8f6c\u6362\u4e3a\u6d6e\u70b9\u6570\u518d\u505a\u6bd4\u8f83\uff0c\u6700\u540e\u5bfc\u81f4\u7d22\u5f15\u5931\u6548\u3002<\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">\u5c3d\u91cf\u628a\u6240\u6709\u5217\u5b9a\u4e49\u4e3a NOT NULL\uff08SQL \u89c4\u8303\u4f18\u96c5\uff09<\/h2>\n\n\n\n<ul class=\"wp-block-list\"><li>NOT NULL \u5217\u66f4\u8282\u7701\u7a7a\u95f4\uff0cNULL \u5217\u9700\u8981\u4e00\u4e2a\u989d\u5916\u5b57\u8282\u4f5c\u4e3a\u5224\u65ad\u662f\u5426\u4e3a NULL \u7684\u6807\u5fd7\u4f4d\u3002<\/li><li>NULL \u5217\u9700\u8981\u6ce8\u610f\u7a7a\u6307\u9488\u95ee\u9898\uff0cNULL \u5217\u5728\u8ba1\u7b97\u548c\u6bd4\u8f83\u7684\u65f6\u5019\uff0c\u9700\u8981\u6ce8\u610f\u7a7a\u6307\u9488\u95ee\u9898\u3002<\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">\u4fee\u6539\u6216\u8005\u5220\u9664SQL\uff0c\u5148\u5199WHERE\u67e5\u4e00\u4e0b\uff0c\u786e\u8ba4\u540e\u518d\u8865\u5145 delete \u6216 update\uff08SQL\u540e\u6094\u836f\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u5c24\u5176\u5728\u64cd\u4f5c\u751f\u4ea7\u7684\u6570\u636e\u65f6\uff0c\u9047\u5230\u4fee\u6539\u6216\u8005\u5220\u9664\u7684 SQL\uff0c\u5148\u52a0\u4e2a where \u67e5\u8be2\u4e00\u4e0b\uff0c\u786e\u8ba4 OK \u4e4b\u540e\uff0c\u518d\u6267\u884c update \u6216\u8005 delete \u64cd\u4f5c\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u51cf\u5c11\u4e0d\u5fc5\u8981\u7684\u5b57\u6bb5\u8fd4\u56de\uff0c\u5982\u4f7f\u7528select &lt;\u5177\u4f53\u5b57\u6bb5&gt; \u4ee3\u66ff select * \uff08SQL\u6027\u80fd\u4f18\u5316\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u53cd\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>select\u00a0*\u00a0from\u00a0employee;<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u6b63\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>select\u00a0id\uff0cname\u00a0from\u00a0employee;<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u7406\u7531\uff1a<\/code><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u8282\u7701\u8d44\u6e90\u3001\u51cf\u5c11\u7f51\u7edc\u5f00\u9500\u3002<\/li><li>\u53ef\u80fd\u7528\u5230\u8986\u76d6\u7d22\u5f15\uff0c\u51cf\u5c11\u56de\u8868\uff0c\u63d0\u9ad8\u67e5\u8be2\u6548\u7387\u3002<\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">\u6240\u6709\u8868\u5fc5\u987b\u4f7f\u7528Innodb\u5b58\u50a8\u5f15\u64ce\uff08SQL\u89c4\u8303\u4f18\u96c5\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Innodb \u652f\u6301\u4e8b\u52a1\uff0c\u652f\u6301\u884c\u7ea7\u9501\uff0c\u66f4\u597d\u7684\u6062\u590d\u6027\uff0c\u9ad8\u5e76\u53d1\u4e0b\u6027\u80fd\u66f4\u597d\uff0c\u6240\u4ee5\u5462\uff0c\u6ca1\u6709\u7279\u6b8a\u8981\u6c42\uff08\u5373 Innodb \u65e0\u6cd5\u6ee1\u8db3\u7684\u529f\u80fd\u5982\uff1a\u5217\u5b58\u50a8\uff0c\u5b58\u50a8\u7a7a\u95f4\u6570\u636e\u7b49\uff09\u7684\u60c5\u51b5\u4e0b\uff0c\u6240\u6709\u8868\u5fc5\u987b\u4f7f\u7528 Innodb \u5b58\u50a8\u5f15\u64ce\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u6570\u636e\u5e93\u548c\u8868\u7684\u5b57\u7b26\u96c6\u7edf\u4e00\u4f7f\u7528 UTF8\uff08SQL\u89c4\u8303\u4f18\u96c5\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u7edf\u4e00\u4f7f\u7528 UTF8 \u7f16\u7801<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u53ef\u4ee5\u907f\u514d\u4e71\u7801\u95ee\u9898<\/li><li>\u53ef\u4ee5\u907f\u514d\uff0c\u4e0d\u540c\u5b57\u7b26\u96c6\u6bd4\u8f83\u8f6c\u6362\uff0c\u5bfc\u81f4\u7684\u7d22\u5f15\u5931\u6548\u95ee\u9898<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u5982\u679c\u662f\u5b58\u50a8\u8868\u60c5\u7684\uff0c\u53ef\u4ee5\u8003\u8651 utf8mb4\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">\u5c3d\u91cf\u4f7f\u7528 varchar \u4ee3\u66ff char\u3002\uff08SQL \u6027\u80fd\u4f18\u5316\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u53cd\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>`deptName`\u00a0char(100)\u00a0DEFAULT\u00a0NULL\u00a0COMMENT\u00a0'\u90e8\u95e8\u540d\u79f0'<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u6b63\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>`deptName`\u00a0varchar(100)\u00a0DEFAULT\u00a0NULL\u00a0COMMENT\u00a0'\u90e8\u95e8\u540d\u79f0'<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u7406\u7531\uff1a<\/code><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u56e0\u4e3a\u9996\u5148\u53d8\u957f\u5b57\u6bb5\u5b58\u50a8\u7a7a\u95f4\u5c0f\uff0c\u53ef\u4ee5\u8282\u7701\u5b58\u50a8\u7a7a\u95f4\u3002<\/li><\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">\u5982\u679c\u4fee\u6539\u5b57\u6bb5\u542b\u4e49\u6216\u5bf9\u5b57\u6bb5\u8868\u793a\u7684\u72b6\u6001\u8ffd\u52a0\u65f6\uff0c\u9700\u8981\u53ca\u65f6\u66f4\u65b0\u5b57\u6bb5\u6ce8\u91ca\u3002 \uff08SQL\u89c4\u8303\u4f18\u96c5\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u8fd9\u4e2a\u70b9\uff0c\u662f\u963f\u91cc\u5f00\u53d1\u624b\u518c\u4e2d\uff0cMysql \u7684\u89c4\u7ea6\u3002\u4f60\u7684\u5b57\u6bb5\uff0c\u5c24\u5176\u662f\u8868\u793a\u679a\u4e3e\u72b6\u6001\u65f6\uff0c\u5982\u679c\u542b\u4e49\u88ab\u4fee\u6539\u4e86\uff0c\u6216\u8005\u72b6\u6001\u8ffd\u52a0\u65f6\uff0c\u4e3a\u4e86\u540e\u9762\u66f4\u597d\u7ef4\u62a4\uff0c\u9700\u8981\u5373\u65f6\u66f4\u65b0\u5b57\u6bb5\u7684\u6ce8\u91ca\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">SQL\u4fee\u6539\u6570\u636e\uff0c\u517b\u6210begin + commit \u4e8b\u52a1\u7684\u4e60\u60ef\uff1b(SQL\u540e\u6094\u836f)<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u6b63\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>begin;update\u00a0account\u00a0set\u00a0balance\u00a0=1000000where\u00a0name\u00a0='\u4e1a\u4f59\u8349';commit;<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u53cd\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>update\u00a0account\u00a0set\u00a0balance\u00a0=1000000where\u00a0name\u00a0='\u4e1a\u4f59\u8349';<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">\u7d22\u5f15\u547d\u540d\u8981\u89c4\u8303\uff0c\u4e3b\u952e\u7d22\u5f15\u540d\u4e3a pk_ \u5b57\u6bb5\u540d\uff1b\u552f\u4e00\u7d22\u5f15\u540d\u4e3a uk _\u5b57\u6bb5\u540d \uff1b \u666e\u901a\u7d22\u5f15\u540d\u5219\u4e3a idx _\u5b57\u6bb5\u540d\u3002\uff08SQL\u89c4\u8303\u4f18\u96c5\uff09<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u8bf4\u660e\uff1a pk_ \u5373 primary key\uff1buk _ \u5373 unique key\uff1bidx _ \u5373 index \u7684\u7b80\u79f0\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">WHERE\u4ece\u53e5\u4e2d\u4e0d\u5bf9\u5217\u8fdb\u884c\u51fd\u6570\u8f6c\u6362\u548c\u8868\u8fbe\u5f0f\u8ba1\u7b97<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">\u5047\u8bbe loginTime \u52a0\u4e86\u7d22\u5f15\u3002<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u53cd\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>select\u00a0userId,loginTime\u00a0from\u00a0loginuser\u00a0where\u00a0Date_ADD(loginTime,Interval\u00a07\u00a0DAY)\u00a0&gt;=now();<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u6b63\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>explain\u00a0\u00a0select\u00a0userId,loginTime\u00a0from\u00a0loginuser\u00a0where\u00a0\u00a0loginTime\u00a0&gt;=\u00a0Date_ADD(NOW(),INTERVAL\u00a0-\u00a07\u00a0DAY);<\/code><\/pre>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"https:\/\/gitee.com\/xmtblog\/img\/raw\/master\/2020\/sql8.png\" alt=\"\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">\u5982\u679c\u4fee\u6539\u66f4\u65b0\u6570\u636e\u8fc7\u591a\uff0c\u8003\u8651\u6279\u91cf\u8fdb\u884c\u3002<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u53cd\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>delete\u00a0from\u00a0account\u00a0\u00a0limit\u00a0100000;<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u6b63\u4f8b\uff1a<\/code><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>for\u00a0each(200\u6b21){\u00a0\u00a0\u00a0delete\u00a0from\u00a0account\u00a0\u00a0limit\u00a0500;}<\/code><\/pre>\n\n\n\n<p class=\"wp-block-paragraph\"><code>\u7406\u7531\uff1a<\/code><\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>\u5927\u6279\u91cf\u64cd\u4f5c\u4f1a\u4f1a\u9020\u6210\u4e3b\u4ece\u5ef6\u8fdf\u3002<\/li><li>\u64cd\u4f5c\u4f1a\u4ea7\u751f\u5927\u4e8b\u52a1\uff0c\u963b\u585e\u3002<\/li><li>\u91cf\u64cd\u4f5c\uff0c\u6570\u636e\u91cf\u8fc7\u5927\uff0c\u4f1a\u628acpu\u6253\u6ee1\u3002<\/li><\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">\u4ee5\u4e0a\u5185\u5bb9\u5e0c\u671b\u5728\u8bfb\u8005\u7684\u7f16\u7a0b\u4e4b\u8def\u4e0a\u6709\u6240\u5e2e\u52a9\uff01<\/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=5123\">MySQL \u7684 21 \u4e2a\u89c4\u8303\u3001\u4f18\u5316\u6700\u4f73\u5b9e\u8df5\uff01<\/a><\/p><!-- <div class=\"bd-reward-stl\"><button id=\"bdRewardBtn\"><span><\/span><\/button><\/div> -->","protected":false},"excerpt":{"rendered":"<p>\u524d\u8a00 \u6bcf\u4e00\u4e2a\u597d\u4e60\u60ef\u90fd\u662f\u4e00\u7b14\u8d22\u5bcc\uff0c\u672c\u6587\u5206 SQL \u540e\u6094\u836f\uff0cSQL \u6027\u80fd\u4f18\u5316\uff0cSQL \u89c4\u8303\u4f18\u96c5\u4e09\u4e2a\u65b9\u5411\uff0c\u5206\u4eab\u5199 S [&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-5123","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\/5123","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=5123"}],"version-history":[{"count":1,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/5123\/revisions"}],"predecessor-version":[{"id":5124,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=\/wp\/v2\/posts\/5123\/revisions\/5124"}],"wp:attachment":[{"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5123"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5123"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.xttblog.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5123"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}