{"id":516,"date":"2020-06-19T23:07:48","date_gmt":"2020-06-19T15:07:48","guid":{"rendered":"https:\/\/www.zeroheart.xyz\/wordpress\/?p=516"},"modified":"2020-06-21T22:34:58","modified_gmt":"2020-06-21T14:34:58","slug":"mysql%e4%bc%98%e5%8c%96%e7%af%87","status":"publish","type":"post","link":"https:\/\/www.zeroheart.xyz\/wordpress\/?p=516","title":{"rendered":"mysql\u4f18\u5316\u7bc7"},"content":{"rendered":"\n<p>\u4e4b\u524d\u770b\u4e86mysql innodb\u7684\u4e66\uff0c\u4e00\u76f4\u4e5f\u6ca1\u6574\u7406\u3002\u5148\u770b\u770b\u522b\u4eba\u7684\u603b\u7ed3\uff0c\u7ed3\u5408\u81ea\u5df1\u770b\u7684\uff0c\u505a\u4e9b\u8bb0\u5f55\u3002<\/p>\n\n\n\n<p>\u4ece\u5b9e\u9645\u4e1a\u52a1\u4e2d\uff0c\u53ef\u4ee5\u53d1\u73b0\uff0c\u5982\u679cjoin\u7684\u8868\u8fc7\u591a\u7684\u8bdd\uff0c\u67e5\u8be2\u901f\u5ea6\u4f1a\u5f88\u6162\u7684\uff0c\u7cfb\u7edf\u4e2d\u7684item\u8868\uff0c\u5c31\u662f\u4f8b\u5b50\uff0c\u4e4b\u524d\u505a\u4e86\u4f18\u5316\uff0c\u5f3a\u5236\u8d70\u7d22\u5f15\u624d\u5feb\u4e86\u4e00\u70b9\uff0c\u4f46\u662f\u5b9e\u9645\u901f\u5ea6\u8fd8\u662f\u4e0d\u592a\u7406\u60f3\u3002<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">1.\u522b\u4eba\u7684\u603b\u7ed3\uff1a<\/h4>\n\n\n\n<p>a.\u8bbe\u8ba1\u826f\u597d\u7684\u6570\u636e\u5e93\u7ed3\u6784\uff0c\u5141\u8bb8\u90e8\u5206\u6570\u636e\u5197\u4f59\uff0c\u5c3d\u91cf\u907f\u514djoin\u67e5\u8be2\uff0c\u63d0\u9ad8\u6548\u7387\u3002<br>b.\u9009\u62e9\u5408\u9002\u7684\u8868\u5b57\u6bb5\u6570\u636e\u7c7b\u578b\u548c\u5b58\u50a8\u5f15\u64ce\uff0c\u9002\u5f53\u7684\u6dfb\u52a0\u7d22\u5f15\u3002<br>c.mysql\u5e93\u4e3b\u4ece\u8bfb\u5199\u5206\u79bb\u3002<br>d.\u627e\u89c4\u5f8b\u5206\u8868\uff0c\u51cf\u5c11\u5355\u8868\u4e2d\u7684\u6570\u636e\u91cf\u63d0\u9ad8\u67e5\u8be2\u901f\u5ea6\u3002<br>e.\u6dfb\u52a0\u7f13\u5b58\u673a\u5236\uff0c\u6bd4\u5982memcached\uff0capc\u7b49\u3002<br>f.\u4e0d\u7ecf\u5e38\u6539\u52a8\u7684\u9875\u9762\uff0c\u751f\u6210\u9759\u6001\u9875\u9762\u3002<br>g.\u4e66\u5199\u9ad8\u6548\u7387\u7684SQL\u3002\u6bd4\u5982 SELECT * FROM TABEL \u6539\u4e3a SELECT field_1, field_2, field_3 FROM TABLE.<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">2.\u4f18\u5316<\/h4>\n\n\n\n<p>\u4f18\u5316\u987a\u5e8f\uff0csql\u8bed\u53e5\u7d22\u5f15\u7ea7\u522b\u7684\u4f18\u5316\u3001\u8868\u7ed3\u6784\u4f18\u5316\u3001\u7cfb\u7edf\u914d\u7f6e\u4f18\u5316\u3001\u786c\u4ef6\u6027\u80fd\u7684\u4f18\u5316\u7b49<\/p>\n\n\n\n<h4 class=\"wp-block-heading\">3.\u5e38\u7528\u7684\u4f18\u5316\u6280\u5de7<\/h4>\n\n\n\n<pre class=\"wp-block-preformatted\">1.\u4f7f\u7528\u67e5\u8be2\u7f13\u5b58\u4f18\u5316\u67e5\u8be2<br>a.SELECT username FROM user WHERE &nbsp; &nbsp;signup_date &gt;= CURDATE()<br>b.SELECT username FROM user WHERE &nbsp; &nbsp;signup_date &gt;= '2014-06-24\u2018<br>\u4e0a\u9762\u4e24\u6761SQL\u8bed\u53e5\u7684\u5dee\u522b\u5c31\u662f CURDATE() \uff0cMySQL\u7684\u67e5\u8be2\u7f13\u5b58\u5bf9\u8fd9\u4e2a\u51fd\u6570\u4e0d\u8d77\u4f5c\u7528\u3002\u6240\u4ee5\uff0c\u50cf NOW() \u548c RAND() \u6216\u662f\u5176\u5b83\u7684\u8bf8\u5982\u6b64\u7c7b\u7684SQL\u51fd\u6570\u90fd\u4e0d\u4f1a\u5f00\u542f\u67e5\u8be2\u7f13\u5b58\uff0c\u56e0\u4e3a\u8fd9\u4e9b\u51fd\u6570\u7684\u8fd4\u56de\u662f\u6613\u53d8\u7684\u3002\u6240\u4ee5\uff0c\u4f60\u6240\u9700\u8981\u7684\u5c31\u662f\u7528\u4e00\u4e2a\u53d8\u91cf\u6765\u4ee3\u66ffMySQL\u7684\u51fd\u6570\uff0c\u4ece\u800c\u5f00\u542f\u7f13\u5b58\u3002<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">2.\u4f7f\u7528EXPLAIN\u5173\u952e\u5b57\u68c0\u6d4b\u67e5\u8be2<br>Explain + sql \u8bed\u53e5\u540e\u9762\u4f1a\u4e13\u95e8\u7528\u4e00\u7bc7\u6765\u8bb2\u4e00\u4e0b\u3002<a href=\"https:\/\/www.zeroheart.xyz\/wordpress\/?p=653\">https:\/\/www.zeroheart.xyz\/wordpress\/?p=653<\/a><br>\u4f7f\u7528\u8fd9\u4e2a\u5173\u952e\u5b57\uff0c\u53ef\u4ee5\u8ba9\u6211\u4eec\u77e5\u9053\u6267\u884c\u4e2d\u7528\u4e86\u4ec0\u4e48\u7d22\u5f15\uff0c\u626b\u63cf\u4e86\u591a\u5c11\u6570\u636e\u7b49\u7b49\u3002\u6839\u636e\u8fd9\u4e2a\uff0c\u53ef\u4ee5\u4f18\u5316\u7d22\u5f15\uff0c\u6216\u8005\u5f3a\u5236\u4f7f\u7528\u67d0\u4e9b\u7d22\u5f15\u3002<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">3.\u5f53\u53ea\u8981\u4e00\u884c\u6570\u636e\u65f6\u4f7f\u7528LIMIT 1<br>\u67e5\u5230\u5230\u4e00\u6761\u7b26\u5408\u6761\u4ef6\u7684\u6570\u636e\u4e4b\u540e\uff0csql\u67e5\u627e\u4f1a\u505c\u6b62\uff0c\u907f\u514d\u65e0\u8c13\u7684\u6d88\u8017\u3002<br><br>limit \u7684\u5176\u4ed6\u4f18\u5316\uff0c\u6211\u4eec\u5e38\u7528\u7684\u5206\u9875\uff0c\u5f53\u9875\u6570\u9760\u540e\uff08\u53d8\u5927\uff09\u7684\u65f6\u5019\uff0c\u5f80\u5f80\u67e5\u8be2\u901f\u5ea6\u5927\u5e45\u4e0b\u964d\u3002sql\u7c7b\u4f3c\u8fd9\u6837<br>select * from test limit 1000000, 100<br>\u8fd9\u6837\u5b50\u7684\u8bed\u53e5\uff0c\u662f\u9700\u8981\u628a\u6570\u636e\u90fd\u67e5\u51fa\u6765\u5728\u4e4b\u540e\u5728\u627e100\u6761\u7684\uff0c\u53ef\u4ee5\u6539\u4e3a\u5176\u4ed6\u5199\u6cd5,\u5e76\u5c3d\u91cf\u5f15\u5bfc\u5ba2\u6237\u4f7f\u7528\u641c\u7d22\u6761\u4ef6\u3002<br>1.select * from tsest where id &gt; (select id from test limit 1000000,1) limit 0, 100;<br>2. SELECT * FROM test a JOIN (SELECT id  FROM test LIMIT 1000000,100) b ON a.id = b.id<br>3.select * from tsest where id between (lastId, lastId+100);<br><\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">4.\u4e3a\u641c\u7d22\u5b57\u6bb5\u5efa\u7acb\u7d22\u5f15<br><br>\u7d22\u5f15\u4e0d\u4e00\u5b9a\u5c31\u662f\u7ed9\u4e3b\u952e\u6216\u8005\u662f\u552f\u4e00\u7684\u5b57\u6bb5\uff0c\u5982\u679c\u5728\u8868\u4e2d\uff0c\u6709\u67d0\u4e2a\u5b57\u6bb5\u7ecf\u5e38\u7528\u6765\u505a\u641c\u7d22\uff0c\u9700\u8981\u5c06\u5176\u5efa\u7acb\u7d22\u5f15\u3002<br> \u7d22\u5f15\u7684\u6709\u5173\u64cd\u4f5c\u5982\u4e0b\uff1a<br> 1.\u521b\u5efa\u7d22\u5f15<br> \u5728\u6267\u884cCREATE TABLE\u8bed\u53e5\u65f6\u53ef\u4ee5\u521b\u5efa\u7d22\u5f15\uff0c\u4e5f\u53ef\u4ee5\u5355\u72ec\u7528CREATE INDEX\u6216ALTER TABLE\u6765\u4e3a\u8868\u589e\u52a0\u7d22\u5f15\u3002<br> 1.1&gt; ALTER TABLE<br> ALTER TABLE \u7528\u6765\u521b\u5efa\u666e\u901a\u7d22\u5f15\u3001\u552f\u4e00\u7d22\u5f15\u3001\u4e3b\u952e\u7d22\u5f15\u548c\u5168\u6587\u7d22\u5f15<br> ALTER TABLE table_name ADD INDEX index_name (column_list);<br> ALTER TABLE table_name ADD UNIQUE (column_list);<br> ALTER TABLE table_name ADD PRIMARY KEY (column_list);<br> ALTER TABLE table_name ADD FULLTEXT (column_list);<br> \u5176\u4e2dtable_name\u662f\u8981\u589e\u52a0\u7d22\u5f15\u540d\u7684\u8868\u540d\uff0ccolumn_list\u6307\u51fa\u5bf9\u54ea\u4e9b\u5217\u5217\u8fdb\u884c\u7d22\u5f15\uff0c\u591a\u5217\u65f6\u5404\u5217\u4e4b\u95f4\u4f7f\u7528\u534a\u89d2\u9017\u53f7\u9694\u5f00\u3002\u7d22\u5f15\u540dindex_name\u662f\u53ef\u9009\u7684\uff0c\u5982\u679c\u4e0d\u6307\u5b9a\u7d22\u5f15\u540d\u79f0\uff0cMySQL\u5c06\u6839\u636e\u7b2c\u4e00\u4e2a\u7d22\u5f15\u5217\u81ea\u52a8\u6307\u5b9a\u7d22\u5f15\u540d\u79f0\uff0c\u53e6\u5916\uff0cALTER TABLE\u5141\u8bb8\u5728\u5355\u4e2a\u8bed\u53e5\u4e2d\u66f4\u6539\u591a\u4e2a\u8868\uff0c\u56e0\u6b64\u53ef\u4ee5\u5728\u540c\u65f6\u521b\u5efa\u591a\u4e2a\u7d22\u5f15\u3002<br> 1.2&gt; CREATE INDEX<br> CREATE INDEX\u53ef\u5bf9\u8868\u589e\u52a0\u666e\u901a\u7d22\u5f15\u6216UNIQUE\u7d22\u5f15\u4ee5\u53ca\u5168\u6587\u7d22\u5f15\uff0c\u4f46\u662f\u4e0d\u53ef\u4ee5\u5bf9\u8868\u589e\u52a0\u4e3b\u952e\u7d22\u5f15<br> CREATE INDEX index_name ON table_name (column_list);<br> CREATE UNIQUE index_name ON table_name (column_list);<br> CREATE FULLTEXT index_name ON table_name (column_list);<br> table_name\u3001index_name\u548ccolumn_list\u5177\u6709\u4e0eALTER TABLE\u8bed\u53e5\u4e2d\u76f8\u540c\u7684\u542b\u4e49\uff0c\u7d22\u5f15\u540d\u5fc5\u987b\u6307\u5b9a\u3002\u53e6\u5916\uff0c\u4e0d\u80fd\u7528CREATE INDEX\u8bed\u53e5\u521b\u5efaPRIMARY KEY\u7d22\u5f15\u3002<br><br><br>2.\u7d22\u5f15\u7c7b\u578b<br> \u666e\u901a\u7d22\u5f15INDEX\uff1a\u9002\u7528\u4e8ename\u3001email\u7b49\u4e00\u822c\u5c5e\u6027<br> \u552f\u4e00\u7d22\u5f15UNIQUE\uff1a\u4e0e\u666e\u901a\u7d22\u5f15\u7c7b\u4f3c\uff0c\u4e0d\u540c\u7684\u662f\u552f\u4e00\u7d22\u5f15\u8981\u6c42\u7d22\u5f15\u5b57\u6bb5\u503c\u5728\u8868\u4e2d\u662f\u552f\u4e00\u7684\uff0c\u8fd9\u4e00\u70b9\u548c\u4e3b\u952e\u7d22\u5f15\u7c7b\u4f3c\uff0c\u4f46\u662f\u4e0d\u540c\u7684\u662f\uff0c\u552f\u4e00\u7d22\u5f15\u5141\u8bb8\u6709\u7a7a\u503c\u3002\u552f\u4e00\u7d22\u5f15\u4e00\u822c\u9002\u7528\u4e8e\u8eab\u4efd\u8bc1\u53f7\u7801\u3001\u7528\u6237\u8d26\u53f7\u7b49\u4e0d\u5141\u8bb8\u6709\u91cd\u590d\u7684\u5c5e\u6027\u5b57\u6bb5\u4e0a\u3002<br> \u4e3b\u952e\u7d22\u5f15\uff1a\u5176\u5b9e\u5c31\u662f\u4e3b\u952e\uff0c\u4e00\u822c\u5728\u5efa\u8868\u65f6\u5c31\u6307\u5b9a\u4e86\uff0c\u4e0d\u9700\u8981\u989d\u5916\u6dfb\u52a0\u3002<br> \u5168\u6587\u68c0\u7d22\uff1a\u53ea\u9002\u7528\u4e8eVARCHAR\u548cText\u7c7b\u578b\u7684\u5b57\u6bb5\u3002<br> \u6ce8\u610f\uff1a\u5168\u6587\u7d22\u5f15\u548c\u666e\u901a\u7d22\u5f15\u662f\u6709\u5f88\u5927\u533a\u522b\u7684\uff0c\u5982\u679c\u5efa\u7acb\u7684\u662f\u666e\u901a\u7d22\u5f15\uff0c\u4e00\u822c\u4f1a\u4f7f\u7528like\u8fdb\u884c\u6a21\u7cca\u67e5\u8be2\uff0c\u53ea\u4f1a\u5bf9\u67e5\u8be2\u5185\u5bb9\u524d\u4e00\u90e8\u5206\u6709\u6548\uff0c\u5373\u53ea\u5bf9\u524d\u9762\u4e0d\u4f7f\u7528\u901a\u914d\u7b26\u7684\u67e5\u8be2\u6709\u6548\uff0c\u5982\u679c\u524d\u540e\u90fd\u6709\u901a\u914d\u7b26\uff0c\u666e\u901a\u7d22\u5f15\u5c06\u4e0d\u4f1a\u8d77\u4f5c\u7528\u3002\u5bf9\u4e8e\u5168\u6587\u7d22\u5f15\u800c\u8a00\u5728\u67e5\u8be2\u65f6\u6709\u81ea\u5df1\u72ec\u7279\u7684\u5339\u914d\u65b9\u5f0f\uff0c\u4f8b\u5982\u6211\u4eec\u5728\u5bf9\u4e00\u7bc7\u6587\u7ae0\u7684\u6807\u9898\u548c\u5185\u5bb9\u8fdb\u884c\u5168\u6587\u7d22\u5f15\u65f6\uff1a<br> ALTER TABLE article ADD FULLTEXT ('title', 'content'); \u5728\u8fdb\u884c\u68c0\u7d22\u65f6\u5c31\u9700\u8981\u4f7f\u7528\u5982\u4e0b\u7684\u8bed\u6cd5\u8fdb\u884c\u68c0\u7d22\uff1a<br> SELECT * FROM article WHERE MATCH('title', 'content') AGAINST ('\u67e5\u8be2\u5b57\u7b26\u4e32');<br> \u5728\u4f7f\u7528\u5168\u6587\u68c0\u7d22\u65f6\u7684\u6ce8\u610f\u4e8b\u9879\uff1a<br> MySql\u81ea\u5e26\u7684\u5168\u6587\u7d22\u5f15\u53ea\u80fd\u7528\u4e8e\u6570\u636e\u5e93\u5f15\u64ce\u4e3aMYISAM\u7684\u6570\u636e\u8868\uff0c\u5982\u679c\u662f\u5176\u4ed6\u6570\u636e\u5f15\u64ce\uff0c\u5219\u5168\u6587\u7d22\u5f15\u4e0d\u4f1a\u751f\u6548\u3002\u6b64\u5916\uff0cMySql\u81ea\u5e26\u7684\u5168\u6587\u7d22\u5f15\u53ea\u80fd\u5bf9\u82f1\u6587\u8fdb\u884c\u5168\u6587\u68c0\u7d22\uff0c\u76ee\u524d\u65e0\u6cd5\u5bf9\u4e2d\u6587\u8fdb\u884c\u5168\u6587\u68c0\u7d22\u3002\u5982\u679c\u9700\u8981\u5bf9\u5305\u542b\u4e2d\u6587\u5728\u5185\u7684\u6587\u672c\u6570\u636e\u8fdb\u884c\u5168\u6587\u68c0\u7d22\uff0c\u6211\u4eec\u9700\u8981\u91c7\u7528Sphinx\uff08\u65af\u82ac\u514b\u65af\uff09\/Coreseek\u6280\u672f\u6765\u5904\u7406\u4e2d\u6587\u3002\u53e6\u5916\u4f7f\u7528MySql\u81ea\u5e26\u7684\u5168\u6587\u7d22\u5f15\u65f6\uff0c\u5982\u679c\u67e5\u8be2\u5b57\u7b26\u4e32\u7684\u957f\u5ea6\u8fc7\u77ed\u5c06\u65e0\u6cd5\u5f97\u5230\u671f\u671b\u7684\u641c\u7d22\u7ed3\u679c\u3002MySql\u5168\u6587\u7d22\u5f15\u6240\u80fd\u627e\u5230\u7684\u8bcd\u9ed8\u8ba4\u6700\u5c0f\u957f\u5ea6\u4e3a4\u4e2a\u5b57\u7b26\u3002\u53e6\u5916\uff0c\u5982\u679c\u67e5\u8be2\u7684\u5b57\u7b26\u4e32\u5305\u542b\u505c\u6b62\u8bcd\uff0c\u90a3\u4e48\u8be5\u505c\u6b62\u8bcd\u5c06\u4f1a\u88ab\u5ffd\u7565\u3002<br><br>3.\u7ec4\u5408\u7d22\u5f15<br>\u7ec4\u5408\u7d22\u5f15\u53c8\u79f0\u591a\u5217\u7d22\u5f15\uff0c\u5c31\u662f\u5efa\u7acb\u7d22\u5f15\u65f6\u6307\u5b9a\u591a\u4e2a\u5b57\u6bb5\u5c5e\u6027\u3002\u6709\u70b9\u7c7b\u4f3c\u4e8e\u5b57\u5178\u76ee\u5f55\uff0c\u6bd4\u5982\u67e5\u8be2 'guo' \u8fd9\u4e2a\u62fc\u97f3\u7684\u5b57\u65f6\uff0c\u9996\u5148\u67e5\u627eg\u5b57\u6bcd\uff0c\u7136\u540e\u5728g\u7684\u68c0\u7d22\u8303\u56f4\u5185\u67e5\u8be2\u7b2c\u4e8c\u4e2a\u5b57\u6bcd\u4e3au\u7684\u5217\u8868\uff0c\u6700\u540e\u5728u\u7684\u8303\u56f4\u5185\u67e5\u627e\u6700\u540e\u4e00\u4e2a\u5b57\u6bcd\u4e3ao\u7684\u5b57\u3002\u6bd4\u5982\u7ec4\u5408\u7d22\u5f15(a,b,c)\uff0cabc\u90fd\u662f\u6392\u597d\u5e8f\u7684\uff0c\u5728\u4efb\u610f\u4e00\u6bb5a\u7684\u4e0b\u9762b\u90fd\u662f\u6392\u597d\u5e8f\u7684\uff0c\u4efb\u4f55\u4e00\u6bb5b\u4e0b\u9762c\u90fd\u662f\u6392\u597d\u5e8f\u7684<br><br>\u7ec4\u5408\u7d22\u5f15\u7684\u751f\u6548\u539f\u5219\u662f &nbsp;\u4ece\u524d\u5f80\u540e\u4f9d\u6b21\u4f7f\u7528\u751f\u6548\uff0c\u5982\u679c\u4e2d\u95f4\u67d0\u4e2a\u7d22\u5f15\u6ca1\u6709\u4f7f\u7528\uff0c\u90a3\u4e48\u65ad\u70b9\u524d\u9762\u7684\u7d22\u5f15\u90e8\u5206\u8d77\u4f5c\u7528\uff0c\u65ad\u70b9\u540e\u9762\u7684\u7d22\u5f15\u6ca1\u6709\u8d77\u4f5c\u7528\uff1b<br><br>\u9020\u6210\u65ad\u70b9\u7684\u539f\u56e0\uff1a<br>\u524d\u8fb9\u7684\u4efb\u610f\u4e00\u4e2a\u7d22\u5f15\u6ca1\u6709\u53c2\u4e0e\u67e5\u8be2\uff0c\u540e\u8fb9\u7684\u5168\u90e8\u4e0d\u751f\u6548\u3002<br>\u524d\u8fb9\u7684\u4efb\u610f\u4e00\u4e2a\u7d22\u5f15\u5b57\u6bb5\u53c2\u4e0e\u7684\u662f\u8303\u56f4\u67e5\u8be2\uff0c\u540e\u9762\u7684\u4e0d\u4f1a\u751f\u6548\u3002<br><br>(0) select * from mytable where a=3 and b=5 and c=4;<br>abc\u4e09\u4e2a\u7d22\u5f15\u90fd\u5728where\u6761\u4ef6\u91cc\u9762\u7528\u5230\u4e86\uff0c\u800c\u4e14\u90fd\u53d1\u6325\u4e86\u4f5c\u7528<br><font color=\"red\">(1) select * from mytable where  c=4 and b=6 and a=3;<br>\u8fd9\u6761\u8bed\u53e5\u4e3a\u4e86\u8bf4\u660e \u7ec4\u5408\u7d22\u5f15\u4e0e\u5728SQL\u4e2d\u7684\u4f4d\u7f6e\u5148\u540e\u65e0\u5173\uff0cwhere\u91cc\u9762\u7684\u6761\u4ef6\u987a\u5e8f\u5728\u67e5\u8be2\u4e4b\u524d\u4f1a\u88abmysql\u81ea\u52a8\u4f18\u5316\uff0c\u6548\u679c\u8ddf\u4e0a\u4e00\u53e5\u4e00\u6837\uff08\u8fd9\u4e2a\u4e0d\u540c\u4eba\u8bf4\u7684\u4e0d\u4e00\u6837\uff0c\u6709\u5f85\u786e\u8ba4\u4e00\u4e0b\uff09<\/font><br>(2) select * from mytable where a=3 and c=7;<br>a\u7528\u5230\u7d22\u5f15\uff0cb\u6ca1\u6709\u7528\uff0c\u6240\u4ee5c\u662f\u6ca1\u6709\u7528\u5230\u7d22\u5f15\u6548\u679c\u7684<br>(3) select * from mytable where a=3 and b&gt;7 and c=3;<br>a\u7528\u5230\u4e86\uff0cb\u4e5f\u7528\u5230\u4e86\uff0cc\u6ca1\u6709\u7528\u5230\uff0c\u8fd9\u4e2a\u5730\u65b9b\u662f\u8303\u56f4\u503c\uff0c\u4e5f\u7b97\u65ad\u70b9\uff0c\u53ea\u4e0d\u8fc7\u81ea\u8eab\u7528\u5230\u4e86\u7d22\u5f15<br>(4) select * from mytable where b=3 and c=4;<br>\u56e0\u4e3aa\u7d22\u5f15\u6ca1\u6709\u4f7f\u7528\uff0c\u6240\u4ee5\u8fd9\u91cc bc\u90fd\u6ca1\u6709\u7528\u4e0a\u7d22\u5f15\u6548\u679c<br>(5) select * from mytable where a&gt;4 and b=7 and c=9;<br> a\u7528\u5230\u4e86  b\u6ca1\u6709\u4f7f\u7528\uff0cc\u6ca1\u6709\u4f7f\u7528<br>(6) select * from mytable where a=3 order by b;<br>a\u7528\u5230\u4e86\u7d22\u5f15\uff0cb\u5728\u7ed3\u679c\u6392\u5e8f\u4e2d\u4e5f\u7528\u5230\u4e86\u7d22\u5f15\u7684\u6548\u679c\uff0c\u524d\u9762\u8bf4\u4e86\uff0ca\u4e0b\u9762\u4efb\u610f\u4e00\u6bb5\u7684b\u662f\u6392\u597d\u5e8f\u7684<br>(7) select * from mytable where a=3 order by c;<br>a\u7528\u5230\u4e86\u7d22\u5f15\uff0c\u4f46\u662f\u8fd9\u4e2a\u5730\u65b9c\u6ca1\u6709\u53d1\u6325\u6392\u5e8f\u6548\u679c\uff0c\u56e0\u4e3a\u4e2d\u95f4\u65ad\u70b9\u4e86\uff0c\u4f7f\u7528 explain \u53ef\u4ee5\u770b\u5230 filesort<br>(8) select * from mytable where b=3 order by a;<br> b\u6ca1\u6709\u7528\u5230\u7d22\u5f15\uff0c\u6392\u5e8f\u4e2da\u4e5f\u6ca1\u6709\u53d1\u6325\u7d22\u5f15\u6548\u679c<br>(9) select * from mytable where a=3 order by a;<br> \u7528\u5230\u7d22\u5f15<br>(10) select * from mytable where a&gt;3 order by b;<br> \u6ca1\u6709\u7528\u5230\u7d22\u5f15<br>(11) select * from mytable where a&gt;3 order by a;<br> \u7528\u5230\u7d22\u5f15<br>(12) select * from mytable where order by a desc , b desc;<br> \u7528\u5230\u7d22\u5f15<br>(13) select * from mytable where order by a desc , b asc;<br> \u6ca1\u6709\u7528\u5230\u7d22\u5f15<br><br><br>\u6ce8\u610f\uff1a\u5728\u67e5\u8be2\u65f6\uff0cMYSQL\u53ea\u80fd\u4f7f\u7528\u4e00\u4e2a\u7d22\u5f15\uff0c\u5982\u679c\u5efa\u7acb\u7684\u662f\u591a\u4e2a\u5355\u5217\u7684\u666e\u901a\u7d22\u5f15\uff0c\u5728\u67e5\u8be2\u65f6\u4f1a\u6839\u636e\u67e5\u8be2\u7684\u7d22\u5f15\u5b57\u6bb5\uff0c\u4ece\u4e2d\u9009\u62e9\u4e00\u4e2a\u9650\u5236\u6700\u4e25\u683c\u7684\u5355\u4f8b\u7d22\u5f15\u8fdb\u884c\u67e5\u8be2\u3002\u522b\u7684\u7d22\u5f15\u90fd\u4e0d\u4f1a\u751f\u6548\u3002<br> 4.\u67e5\u770b\u7d22\u5f15<br> mysql&gt; show index from tblname;<br> mysql&gt; show keys from tblname;<br> 5.\u5220\u9664\u7d22\u5f15<br> \u5220\u9664\u7d22\u5f15\u7684mysql\u683c\u5f0f :DORP INDEX IndexName ON tab_name\uff1b<br> <br>like\u7684\u7d22\u5f15\u89c4\u5f8b\uff1a<br>LIKE\u4ee5%\u5f00\u5934\u4f1a\u5bfc\u81f4\u7d22\u5f15\u5931\u6548\uff1b\u4f7f\u7528\u8986\u76d6\u7d22\u5f15\u89e3\u51b3\u4e4b\u3002<br>\u5927\u6982\u662f\u8bf4\uff0c\u5982\u679c\u67d0\u4e2a\u5b57\u6bb5\u6709\u666e\u901a\u7d22\u5f15\uff0c\u6211\u4eec\u5229\u7528\u8fd9\u4e2a\u5b57\u6bb5\u6a21\u7cca\u67e5\u8be2\u65f6\uff0c\u5982\u679c\u4f7f\u7528\u524d\u7f00\u6216\u8005\u5168\u5339\u914d\uff0c%xx\u6216\u8005%xx%\uff0c\u90fd\u4e0d\u4f1a\u90fd\u7d22\u5f15\uff0c\u53ea\u6709xx%\u53ef\u4ee5\uff0c\u8fd9\u65f6\u5019\uff0c\u5982\u679c\u6709\u5176\u4ed6\u5b57\u6bb5\u548c\u8fd9\u4e2a\u5b57\u6bb5\u5efa\u7acb\u8054\u5408\u7d22\u5f15\uff0c\u67e5\u8be2\u8fd9\u4e2a\u5176\u4ed6\u5b57\u6bb5\u7684\u65f6\u5019\uff0c\u65e0\u8bba\u600e\u4e48\u90fd\u4f1a\u8d70\u7d22\u5f15\uff0c\u67e5\u7d22\u5f15\u5b57\u6bb5\u4e4b\u5916\u7684\u5b57\u6bb5\uff0c\u4f9d\u7136\u4e0d\u884c\u3002<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">5.\u5728join\u8868\u7684\u65f6\u5019\u4f7f\u7528\u76f8\u5f53\u7c7b\u578b\u7684\u5217\uff0c\u5e76\u5c06\u5176\u7d22\u5f15<br>SELECT company_name FROM users LEFT JOIN companies ON (users.state = companies.state) WHERE users.id = \u201cuser_id\u201d<br> \u4e24\u4e2a state \u5b57\u6bb5\u5e94\u8be5\u662f\u88ab\u5efa\u8fc7\u7d22\u5f15\u7684\uff0c\u800c\u4e14\u5e94\u8be5\u662f\u76f8\u5f53\u7684\u7c7b\u578b\uff0c\u76f8\u540c\u7684\u5b57\u7b26\u96c6\u3002<br><\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">6.\u5207\u8bb0\u4e0d\u8981\u4f7f\u7528ORDER BY RAND()<br> \u5982\u679c\u4f60\u771f\u7684\u60f3\u628a\u8fd4\u56de\u7684\u6570\u636e\u884c\u6253\u4e71\u4e86\uff0c\u4f60\u6709N\u79cd\u65b9\u6cd5\u53ef\u4ee5\u8fbe\u5230\u8fd9\u4e2a\u76ee\u7684\u3002\u8fd9\u6837\u4f7f\u7528\u53ea\u8ba9\u4f60\u7684\u6570\u636e\u5e93\u7684\u6027\u80fd\u5448\u6307\u6570\u7ea7\u7684\u4e0b\u964d\u3002\u8fd9\u91cc\u7684\u95ee\u9898\u662f\uff1aMySQL\u4f1a\u4e0d\u5f97\u4e0d\u53bb\u6267\u884cRAND()\u51fd\u6570\uff08\u5f88\u8017CPU\u65f6\u95f4\uff09\uff0c\u800c\u4e14\u8fd9\u662f\u4e3a\u4e86\u6bcf\u4e00\u884c\u8bb0\u5f55\u53bb\u8bb0\u884c\uff0c\u7136\u540e\u518d\u5bf9\u5176\u6392\u5e8f\u3002\u5c31\u7b97\u662f\u4f60\u7528\u4e86Limit 1\u4e5f\u65e0\u6d4e\u4e8e\u4e8b\uff08\u56e0\u4e3a\u8981\u6392\u5e8f\uff09 <br><\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">7.\u907f\u514d\u4f7f\u7528SELECT *<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">8.\u6c38\u8fdc\u4e3a\u6bcf\u5f20\u8868\u8bbe\u7f6e\u4e00\u4e2aID\u4e3b\u952e<br>\u6211\u4eec\u5e94\u8be5\u4e3a\u6570\u636e\u5e93\u91cc\u7684\u6bcf\u5f20\u8868\u90fd\u8bbe\u7f6e\u4e00\u4e2aID\u505a\u4e3a\u5176\u4e3b\u952e\uff0c\u800c\u4e14\u6700\u597d\u7684\u662f\u4e00\u4e2aINT\u578b\u7684\uff08\u63a8\u8350\u4f7f\u7528UNSIGNED\uff09\uff0c\u5e76\u8bbe\u7f6e\u4e0a\u81ea\u52a8\u589e\u52a0\u7684 AUTO_INCREMENT\u6807\u5fd7\u3002 \u5c31\u7b97\u662f\u6211\u4eec users \u8868\u6709\u4e00\u4e2a\u4e3b\u952e\u53eb \u201cemail\u201d\u7684\u5b57\u6bb5\uff0c\u6211\u4eec\u4e5f\u522b\u8ba9\u5b83\u6210\u4e3a\u4e3b\u952e\u3002\u4f7f\u7528 VARCHAR \u7c7b\u578b\u6765\u5f53\u4e3b\u952e\u4f1a\u4f7f\u7528\u5f97\u6027\u80fd\u4e0b\u964d\u3002\u53e6\u5916\uff0c\u5728\u6211\u4eec\u7684\u7a0b\u5e8f\u4e2d\uff0c\u6211\u4eec\u5e94\u8be5\u4f7f\u7528\u8868\u7684ID\u6765\u6784\u9020\u6211\u4eec\u7684\u6570\u636e\u7ed3\u6784\u3002 \u800c\u4e14\uff0c\u5728MySQL\u6570\u636e\u5f15\u64ce\u4e0b\uff0c\u8fd8\u6709\u4e00\u4e9b\u64cd\u4f5c\u9700\u8981\u4f7f\u7528\u4e3b\u952e\uff0c\u5728\u8fd9\u4e9b\u60c5\u51b5\u4e0b\uff0c\u4e3b\u952e\u7684\u6027\u80fd\u548c\u8bbe\u7f6e\u53d8\u5f97\u975e\u5e38\u91cd\u8981\uff0c\u6bd4\u5982\uff0c\u96c6\u7fa4\uff0c\u5206\u533a\u2026\u2026 \u5728\u8fd9\u91cc\uff0c\u53ea\u6709\u4e00\u4e2a\u60c5\u51b5\u662f\u4f8b\u5916\uff0c\u90a3\u5c31\u662f\u201c\u5173\u8054\u8868\u201d\u7684\u201c\u5916\u952e\u201d\uff0c\u4e5f\u5c31\u662f\u8bf4\uff0c\u8fd9\u4e2a\u8868\u7684\u4e3b\u952e\uff0c\u901a\u8fc7\u82e5\u5e72\u4e2a\u522b\u7684\u8868\u7684\u4e3b\u952e\u6784\u6210\u3002\u6211\u4eec\u628a\u8fd9\u4e2a\u60c5\u51b5\u53eb\u505a\u201c\u5916\u952e\u201d\u3002\u6bd4\u5982\uff1a\u6709\u4e00\u4e2a\u201c\u5b66\u751f\u8868\u201d\u6709\u5b66\u751f\u7684ID\uff0c\u6709\u4e00\u4e2a\u201c\u8bfe\u7a0b\u8868\u201d\u6709\u8bfe\u7a0bID\uff0c\u90a3\u4e48\uff0c\u201c\u6210\u7ee9\u8868\u201d\u5c31\u662f\u201c\u5173\u8054\u8868\u201d\u4e86\uff0c\u5176\u5173\u8054\u4e86\u5b66\u751f\u8868\u548c\u8bfe\u7a0b\u8868\uff0c\u5728\u6210\u7ee9\u8868\u4e2d\uff0c\u5b66\u751fID\u548c\u8bfe\u7a0bID\u53eb\u201c\u5916\u952e\u201d\u5176\u5171\u540c\u7ec4\u6210\u4e3b\u952e\u3002 <br><\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">9.\u4f7f\u7528ENUM\u800c\u4e0d\u662fVARCHAR<br> ENUM \u7c7b\u578b\u662f\u975e\u5e38\u5feb\u548c\u7d27\u51d1\u7684\u3002\u5728\u5b9e\u9645\u4e0a\uff0c\u5176\u4fdd\u5b58\u7684\u662f TINYINT\uff0c\u4f46\u5176\u5916\u8868\u4e0a\u663e\u793a\u4e3a\u5b57\u7b26\u4e32\u3002\u8fd9\u6837\u4e00\u6765\uff0c\u7528\u8fd9\u4e2a\u5b57\u6bb5\u6765\u505a\u4e00\u4e9b\u9009\u9879\u5217\u8868\u53d8\u5f97\u76f8\u5f53\u7684\u5b8c\u7f8e\u3002 \u5982\u679c\u6211\u4eec\u6709\u4e00\u4e2a\u5b57\u6bb5\uff0c\u6bd4\u5982\u201c\u6027\u522b\u201d\uff0c\u201c\u56fd\u5bb6\u201d\uff0c\u201c\u6c11\u65cf\u201d\uff0c\u201c\u72b6\u6001\u201d\u6216\u201c\u90e8\u95e8\u201d\uff0c\u6211\u4eec\u77e5\u9053\u8fd9\u4e9b\u5b57\u6bb5\u7684\u53d6\u503c\u662f\u6709\u9650\u800c\u4e14\u56fa\u5b9a\u7684\uff0c\u90a3\u4e48\uff0c\u6211\u4eec\u5e94\u8be5\u4f7f\u7528 ENUM \u800c\u4e0d\u662f VARCHAR\u3002<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">10.\u5c3d\u53ef\u80fd\u7684\u4e0d\u8981\u8d4b\u503c\u4e3aNULL mysql \u91cc\u9762\u6709\u5927\u5751\uff0c\u7cfb\u7edf\u4e2d\u6709\u5f88\u591ais null or ='' or = '\u4f7f\u7528'\u7684\u4ee3\u7801\u5c31\u662f\u8fd9\u4e2a\u4f7f\u7528\u4e0d\u5f53\u9020\u6210\u7684\u3002<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">11.\u56fa\u5b9a\u957f\u5ea6\u7684\u8868\u4f1a\u66f4\u5feb\u3002\u6ca1\u6709\u5b9e\u8df5\u8fc7\uff0c\u4e00\u822c\u4e0d\u8fd9\u4e48\u7528<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">12.\u5782\u76f4\u5206\u5272<br>\u201c\u5782\u76f4\u5206\u5272\u201d\u662f\u4e00\u79cd\u628a\u6570\u636e\u5e93\u4e2d\u7684\u8868\u6309\u5217\u53d8\u6210\u51e0\u5f20\u8868\u7684\u65b9\u6cd5\uff0c\u8fd9\u6837\u53ef\u4ee5\u964d\u4f4e\u8868\u7684\u590d\u6742\u5ea6\u548c\u5b57\u6bb5\u7684\u6570\u76ee\uff0c\u4ece\u800c\u8fbe\u5230\u4f18\u5316\u7684\u76ee\u7684\u3002<br><\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">13.\u62c6\u5206\u5927\u7684DELETE\u6216INSERT<br>\u5982\u679c\u6211\u4eec\u9700\u8981\u5728\u4e00\u4e2a\u5728\u7ebf\u7684\u7f51\u7ad9\u4e0a\u53bb\u6267\u884c\u4e00\u4e2a\u5927\u7684 DELETE \u6216 INSERT \u67e5\u8be2\uff0c\u6211\u4eec\u9700\u8981\u975e\u5e38\u5c0f\u5fc3\uff0c\u8981\u907f\u514d\u6211\u4eec\u7684\u64cd\u4f5c\u8ba9\u6211\u4eec\u7684\u6574\u4e2a\u7f51\u7ad9\u505c\u6b62\u76f8\u5e94\u3002\u56e0\u4e3a\u8fd9\u4e24\u4e2a\u64cd\u4f5c\u662f\u4f1a\u9501\u8868\u7684\uff0c\u8868\u4e00\u9501\u4f4f\u4e86\uff0c\u522b\u7684\u64cd\u4f5c\u90fd\u8fdb\u4e0d\u6765\u4e86\u3002Apache \u4f1a\u6709\u5f88\u591a\u7684\u5b50\u8fdb\u7a0b\u6216\u7ebf\u7a0b\u3002\u6240\u4ee5\uff0c\u5176\u5de5\u4f5c\u8d77\u6765\u76f8\u5f53\u6709\u6548\u7387\uff0c\u800c\u6211\u4eec\u7684\u670d\u52a1\u5668\u4e5f\u4e0d\u5e0c\u671b\u6709\u592a\u591a\u7684\u5b50\u8fdb\u7a0b\uff0c\u7ebf\u7a0b\u548c\u6570\u636e\u5e93\u94fe\u63a5\uff0c\u8fd9\u662f\u6781\u5927\u7684\u5360\u670d\u52a1\u5668\u8d44\u6e90\u7684\u4e8b\u60c5\uff0c\u5c24\u5176\u662f\u5185\u5b58\u3002\u5982\u679c\u6211\u4eec\u628a\u6211\u4eec\u7684\u8868\u9501\u4e0a\u4e00\u6bb5\u65f6\u95f4\uff0c\u6bd4\u598230\u79d2\u949f\uff0c\u90a3\u4e48\u5bf9\u4e8e\u4e00\u4e2a\u6709\u5f88\u9ad8\u8bbf\u95ee\u91cf\u7684\u7ad9\u70b9\u6765\u8bf4\uff0c\u8fd930\u79d2\u6240\u79ef\u7d2f\u7684\u8bbf\u95ee\u8fdb\u7a0b\/\u7ebf\u7a0b\uff0c\u6570\u636e\u5e93\u94fe\u63a5\uff0c\u6253\u5f00\u7684\u6587\u4ef6\u6570\uff0c\u53ef\u80fd\u4e0d\u4ec5\u4ec5\u4f1a\u8ba9\u6211\u4eec\u7684WEB\u670d\u52a1Crash\uff0c\u8fd8\u53ef\u80fd\u4f1a\u8ba9\u6211\u4eec\u7684\u6574\u53f0\u670d\u52a1\u5668\u9a6c\u4e0a\u639b\u4e86\u3002\u6240\u4ee5\u5728\u4f7f\u7528\u65f6\u4f7f\u7528LIMIT\u63a7\u5236\u6570\u91cf\u64cd\u4f5c\u8bb0\u5f55\u7684\u6570\u91cf\u3002<br>limit\u662f\u4e2a\u597d\u4e1c\u897f<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">14.\u8d8a\u5c0f\u7684\u5217\u4f1a\u8d8a\u5feb\uff0c\u5b57\u6bb5\u7c7b\u578b\u8bbe\u7f6e\u8981\u8003\u8651<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">15.\u9009\u62e9\u6b63\u786e\u7684\u5b58\u50a8\u5f15\u64ce,5.5\u540e\u7684\u9ed8\u8ba4\u5f15\u64ce\u662finnodb\uff0c\u63d0\u4f9b\u4e8b\u52a1\uff0c\u4e00\u81f4\u6027\u4e0d\u9501\u5b9a\u8bfb\u7b49\u3002<br><\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">16.\u6ce8\u610f\u6570\u636e\u5e93\u94fe\u63a5\u7684\u4f18\u5316<br><\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">17.\u5728\u67e5\u8be2\u8bed\u53e5\u91cc\u9762\uff0c\u4e0d\u8981\u7528\u52a8\u6001\u8ba1\u7b97\uff0c\u6bd4\u5982 f_quantity - 100 = 10;<br>\u5e94\u8be5\u76f4\u63a5\u5199f_quantity=110,\u8fd9\u662f\u4e2a\u6781\u7aef\u7684\u4f8b\u5b50\uff0c\u8981\u8868\u8fbe\u7684\u5c31\u662f\u4e0d\u8981\u8ba1\u7b97\u540e\u5728\u67e5\u8be2\u3002<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">18.count(*)\u4f1a\u5ffd\u7565\u6240\u6709\u7684\u5217\uff0c\u76f4\u63a5\u7edf\u8ba1\u6240\u6709\u5217\u6570\uff0c\u4e0d\u8981\u4f7f\u7528count(\u5217\u540d)<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">19.\u786e\u4fddGROUP BY\u548cORDER BY\u53ea\u6709\u4e00\u4e2a\u8868\u4e2d\u7684\u5217\uff0c\u8fd9\u6837MySQL\u624d\u6709\u53ef\u80fd\u4f7f\u7528\u7d22\u5f15<br><\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">20. \u7528exists\u4ee3\u66ffin\uff0cnot exists\u4ee3\u66ffnot in\uff0c\u6548\u7387\u4f1a\u66f4\u597d<br><\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">21.\u5e94\u5c3d\u91cf\u907f\u514d\u5728 where \u5b50\u53e5\u4e2d\u4f7f\u7528!=\u6216&lt;&gt;\u64cd\u4f5c\u7b26\uff0c\u5426\u5219\u5f15\u64ce\u5c06\u653e\u5f03\u4f7f\u7528\u7d22\u5f15\u800c\u8fdb\u884c\u5168\u8868\u626b\u63cf\u3002<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">22.\u5e94\u5c3d\u91cf\u907f\u514d\u5728 where \u5b50\u53e5\u4e2d\u4f7f\u7528or\u6765\u8fde\u63a5\u6761\u4ef6\uff0c\u5426\u5219\u5c06\u5bfc\u81f4\u5f15\u64ce\u653e\u5f03\u4f7f\u7528\u7d22\u5f15\u800c\u8fdb\u884c\u5168\u8868\u626b\u63cf\uff0c\u5982\uff1a<br>select id from t where num=10 or num=20<br>-- \u53ef\u4ee5\u8fd9\u6837\u67e5\u8be2\uff1a<br>select id from t where num=10 union all select id from t where num=20<br>in&nbsp;\u548c not in \u4e5f\u8981\u614e\u7528\uff0c\u5426\u5219\u4f1a\u5bfc\u81f4\u5168\u8868\u626b\u63cf\uff0c\u5982\uff1a<br>select id from t where num in(1,2,3)<br>-- \u5bf9\u4e8e\u8fde\u7eed\u7684\u6570\u503c\uff0c\u80fd\u7528 between \u5c31\u4e0d\u8981\u7528 in \u4e86\uff1a<br>select id from t where num between 1 and 3<\/pre>\n\n\n\n<pre class=\"wp-block-preformatted\">23.\u5e94\u5c3d\u91cf\u907f\u514d\u5728 where \u5b50\u53e5\u4e2d\u5bf9\u5b57\u6bb5\u8fdb\u884c null \u503c\u5224\u65ad\uff0c\u5426\u5219\u5c06\u5bfc\u81f4\u5f15\u64ce\u653e\u5f03\u4f7f\u7528\u7d22\u5f15\u800c\u8fdb\u884c\u5168\u8868\u626b\u63cf\uff0c\u5982\uff1a<br>select id from t where num is null<br>-- \u53ef\u4ee5\u5728num\u4e0a\u8bbe\u7f6e\u9ed8\u8ba4\u503c0\uff0c\u786e\u4fdd\u8868\u4e2dnum\u5217\u6ca1\u6709null\u503c\uff0c\u7136\u540e\u8fd9\u6837\u67e5\u8be2\uff1a<br>select id from t where num=0<\/pre>\n\n\n\n<p><\/p>\n\n\n\n<p>\u672c\u6587\u76ee\u524d\u5927\u591a\u53c2\u8003\u4ee5\u4e0b\u6587\u7ae0\uff0c\u8fd8\u6709\u5927\u91cf\u7684\u6280\u5de7\u548c\u8be6\u7ec6\u4f7f\u7528\u6ca1\u6d89\u53ca\uff0c\u4f1a\u6301\u7eed\u8865\u5145\u5b8c\u5584\u6b64\u6587\u7ae0\u3002<\/p>\n\n\n\n<p><\/p>\n\n\n\n<p><a href=\"https:\/\/www.cnblogs.com\/yhgn\/p\/11210130.html\">https:\/\/www.cnblogs.com\/yhgn\/p\/11210130.html<\/a><\/p>\n\n\n\n<p><a href=\"https:\/\/blog.csdn.net\/u013087513\/java\/article\/details\/77899412\">https:\/\/blog.csdn.net\/u013087513\/java\/article\/details\/77899412<\/a><\/p>\n\n\n\n<p><a href=\"https:\/\/blog.csdn.net\/madongyu1259892936\/article\/details\/98978068\">https:\/\/blog.csdn.net\/madongyu1259892936\/article\/details\/98978068<\/a><\/p>\n\n\n\n<p><a href=\"https:\/\/zhuanlan.zhihu.com\/p\/126247848\">https:\/\/zhuanlan.zhihu.com\/p\/126247848<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4e4b\u524d\u770b\u4e86mysql innodb\u7684\u4e66\uff0c\u4e00\u76f4\u4e5f\u6ca1\u6574\u7406\u3002\u5148\u770b\u770b\u522b\u4eba\u7684\u603b\u7ed3\uff0c\u7ed3\u5408\u81ea\u5df1\u770b\u7684\uff0c\u505a\u4e9b\u8bb0\u5f55\u3002 \u4ece\u5b9e\u9645\u4e1a\u52a1\u4e2d\uff0c [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12],"tags":[],"_links":{"self":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/516"}],"collection":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=516"}],"version-history":[{"count":112,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/516\/revisions"}],"predecessor-version":[{"id":671,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/516\/revisions\/671"}],"wp:attachment":[{"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=516"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=516"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.zeroheart.xyz\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=516"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}