{"id":1899,"date":"2019-04-21T14:43:53","date_gmt":"2019-04-21T06:43:53","guid":{"rendered":"https:\/\/www.yusian.com\/blog\/?p=1899"},"modified":"2020-12-02T14:53:26","modified_gmt":"2020-12-02T06:53:26","slug":"dql%e5%b8%b8%e7%94%a8%e6%93%8d%e4%bd%9c%e5%8f%8a%e5%b8%b8%e8%a7%81%e9%97%ae%e9%a2%98","status":"publish","type":"post","link":"https:\/\/www.yusian.com\/blog\/database\/2019\/04\/21\/1443531899.html","title":{"rendered":"DQL\u5e38\u7528\u64cd\u4f5c\u53ca\u5e38\u89c1\u95ee\u9898"},"content":{"rendered":"<p><strong>DQL: Database Query Language<\/strong><\/p>\n<h3>1\u3001\u67e5\u8be2\u67d0\u5b57\u6bb5\u53bb\u91cd\u590d<\/h3>\n<ul>\n<li>select distinct xxxx from xxxx<\/li>\n<\/ul>\n<h3>2\u3001\u5408\u5e76\u5b57\u6bb5\u67e5\u8be2\u51fd\u6570concat( )\u3001concat_ws( )<\/h3>\n<ul>\n<li>select concat(user_name, password) from user;<\/li>\n<li>select concat(user_name, password) as user_name_email from user;<\/li>\n<li>select concat_ws(\u2018->\u2019, user_name, password) from user; \/\/ \u67e5\u8be2\u7ed3\u679c\u7528\u2019->\u2019\u5206\u9694\u7b26\u9694\u5f00<br \/>\n<!--more--><\/li>\n<\/ul>\n<h3>3\u3001\u5408\u5e76\u5b57\u6bb5\u53bb\u91cd\u590d<\/h3>\n<ul>\n<li>select distinct concat(user_name, password) from user; \/\/ \u5408\u5e76\u540e\u7684\u7ed3\u679c\u53bb\u91cd\u590d<\/li>\n<\/ul>\n<h3>4\u3001as\u7684\u4f7f\u7528<\/h3>\n<ul>\n<li>select user_name as xxxx from user;\/\/ \u5b57\u6bb5\u540d\u5c06\u4ee5xxx\u663e\u793a<\/li>\n<\/ul>\n<h3>5\u3001\u5e38\u7528\u7684\u51e0\u4e2a\u51fd\u6570<\/h3>\n<ul>\n<li>count( )\uff0c\u8ba1\u6570\n<ul>\n<li>select count(*) from user; \/\/ \u8ba1\u7b97\u6570\u636e\u603b\u6570<\/li>\n<\/ul>\n<\/li>\n<li>sum( )\uff0c\u6c42\u548c\n<ul>\n<li>select sum(age) from user; \/\/ \u5bf9age\u5217\u6c42\u548c<\/li>\n<\/ul>\n<\/li>\n<li>avg( )\uff0c\u6c42\u5e73\u5747\u503c\n<ul>\n<li>select avg(age) from user; \/\/ \u6c42age\u5e73\u5747\u503c<\/li>\n<\/ul>\n<\/li>\n<li>max( )\u3001min( )\uff0c\u6700\u5927\u503c\u6700\u5c0f\u503c\n<ul>\n<li>select max(age) from user;<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h3>6\u3001group by \u62a5\u9519\u7684\u95ee\u9898<\/h3>\n<pre><code class=\"language-sql line-numbers\">mysql&gt; select * from user group by sex;\nERROR 1055 (42000): Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'sian.user.id' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by\n<\/code><\/pre>\n<p>\u8bdd\u8bf4\u8fd9\u4e2a\u95ee\u9898\u662fmysql\u7684\u67d0\u4e2a\u6a21\u5f0f\u9650\u5236\u4e86group by\u7684\u4f7f\u7528\uff0c\u4f7f\u7528select @@global.sql_mode\u53ef\u4ee5\u67e5\u770b\uff1b<\/p>\n<pre><code class=\"language-sql line-numbers\">mysql&gt; select @@global.sql_mode;\n+---------------------------------------------------------------------------------------------------------------------------+\n| @@global.sql_mode                                                                                                                         |\n+---------------------------------------------------------------------------------------------------------------------------+\n|  ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |\n+-------------------------------------------------------------------------------------------------------------------------------------------+\n1 row in set (0.00 sec)\n<\/code><\/pre>\n<p>\u901a\u8fc7set @@global.sql_mode\u7684\u65b9\u5f0f\u5c06\u7b2c\u4e00\u4e2aONLY_FULL_GROUP_BY\u53bb\u6389<\/p>\n<pre><code class=\"language-sql line-numbers\">mysql&gt; select @@global.sql_mode;\n+------------------------------------------------------------------------------------------------------------------------+\n| @@global.sql_mode                                                                                                      |\n+------------------------------------------------------------------------------------------------------------------------+\n| STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |\n+------------------------------------------------------------------------------------------------------------------------+\n1 row in set (0.01 sec)\n<\/code><\/pre>\n<p><strong>\u6ce8\u610f\uff1a\u8fd9\u4e2a\u65f6\u5019\u53ef\u80fd\u8fd8\u6ca1\u6709\u751f\u6548\uff0c\u9000\u51famysql\uff0c\u9700\u8981\u91cd\u65b0\u767b\u5f55\u624d\u884c\uff01\uff01<\/strong><\/p>\n<h3>7\u3001\u5185\u8fde\u67e5\u8be2<\/h3>\n<ul>\n<li>\u4e24\u4e2a\u8868\u4e2d\u6709\u67d0\u4e2a\u5b57\u6bb5\u5177\u4f53\u6709\u76f8\u5173\u8054\u6027\uff0c\u901a\u8fc7\u4e24\u4e2a\u8868\u4e2d\u8be5\u5b57\u6bb5\u7684\u5173\u7cfb\uff0c\u67e5\u8be2\u4e24\u8868\u6570\u636e\uff1b<\/li>\n<li>user\u8868\u4e2d\u6709\u7528\u6237\u7684\u76f8\u5173\u4fe1\u606f\uff0cmark\u8868\u4e2d\u6709\u6210\u7ee9\u7684\u76f8\u5173\u4fe1\u606f\uff0cmark\u8868\u4e2d\u7684user_id\u4e0euser\u8868\u4e2d\u7684id\u76f8\u5173\u8054\n<pre><code class=\"language-sql line-numbers\">mysql&gt; select u.id, u.user_name, u.sex, m.mark from user as u inner join mark as m where u.id = m.user_id;\n+----+-----------+-----+------+\n| id | user_name | sex | mark |\n+----+-----------+-----+------+\n|  1 | sian      | \u7537  |   90 |\n|  2 | \u4f59\u897f\u5b89     | \u7537  |   88 |\n|  3 | Jack      | \u7537  |   89 |\n|  4 | Rose      | \u5973  |   92 |\n|  5 | Sim       | \u5973  |  100 |\n|  6 | Tony      | \u7537  |   77 |\n+----+-----------+-----+------+\n6 rows in set (0.00 sec)\n<\/code><\/pre>\n<\/li>\n<li>\u7b80\u5316\u8bed\u53e5\n<pre><code class=\"language-sql line-numbers\">mysql&gt; select user.id, user_name, sex, mark from user, mark where user.id = mark.user_id;\n+----+-----------+-----+------+\n| id | user_name | sex | mark |\n+----+-----------+-----+------+\n|  1 | sian      | \u7537  |   90 |\n|  2 | \u4f59\u897f\u5b89     | \u7537  |   88 |\n|  3 | Jack      | \u7537  |   89 |\n|  4 | Rose      | \u5973  |   92 |\n|  5 | Sim       | \u5973  |  100 |\n|  6 | Tony      | \u7537  |   77 |\n+----+-----------+-----+------+\n6 rows in set (0.00 sec)\n<\/code><\/pre>\n<\/li>\n<\/ul>\n<h3>8\u3001\u5de6\u8fde\u63a5\u3001\u53f3\u8fde\u63a5\u67e5\u8be2<\/h3>\n<ul>\n<li>\u5de6\u8fde\u63a5\u4ee5\u5de6\u8868\u4e3a\u57fa\u51c6\uff0c\u53f3\u8fde\u63a5\u4ee5\u53f3\u8868\u6570\u636e\u4e3a\u57fa\u51c6\n<pre><code class=\"language-sql line-numbers\">mysql&gt; select user.id, user_name, sex, mark from user left join mark on user.id = mark.user_id;\n+----+-----------+-----+------+\n| id | user_name | sex | mark |\n+----+-----------+-----+------+\n|  1 | sian      | \u7537  |   90 |\n|  2 | \u4f59\u897f\u5b89     | \u7537  |   88 |\n|  4 | Rose      | \u5973  |   92 |\n|  5 | Sim       | \u5973  |  100 |\n|  6 | Tony      | \u7537  |   77 |\n|  3 | Jack      | \u7537  | NULL |\n+----+-----------+-----+------+\n6 rows in set (0.00 sec)\n\nmysql&gt; select user.id, user_name, sex, mark from user right join mark on user.id = mark.user_id;\n+------+-----------+------+------+\n| id   | user_name | sex  | mark |\n+------+-----------+------+------+\n|    1 | sian      | \u7537   |   90 |\n|    2 | \u4f59\u897f\u5b89     | \u7537   |   88 |\n|    4 | Rose      | \u5973   |   92 |\n|    5 | Sim       | \u5973   |  100 |\n|    6 | Tony      | \u7537   |   77 |\n| NULL | NULL      | NULL |   99 |\n+------+-----------+------+------+\n5 rows in set (0.00 sec)\n<\/code><\/pre>\n<\/li>\n<\/ul>\n<h3>9\u3001\u8054\u5408\u67e5\u8be2<\/h3>\n<ul>\n<li>union\u5173\u952e\u5b57\n<pre><code class=\"language-sql line-numbers\">mysql&gt; select user_name from user union select mark from mark;\n+-----------+\n| user_name |\n+-----------+\n| sian      |\n| \u4f59\u897f\u5b89     |\n| Jack      |\n| Rose      |\n| Sim       |\n| Tony      |\n| 90        |\n| 88        |\n| 92        |\n| 100       |\n| 77        |\n| 99        |\n+-----------+\n12 rows in set (0.00 sec)\n<\/code><\/pre>\n<\/li>\n<li>union\u6765\u4ee3\u66ffwhere\u6761\u4ef6\u4e2d\u7684or\n<pre><code class=\"language-sql line-numbers\">mysql&gt; select id, user_name, email from user where id = 2 or id = 4;\n+----+-----------+-----------------+\n| id | user_name | email           |\n+----+-----------+-----------------+\n|  2 | \u4f59\u897f\u5b89     | yusian@163.com  |\n|  4 | Rose      | rose@yusian.com |\n+----+-----------+-----------------+\n2 rows in set (0.00 sec)\n\nmysql&gt; select id, user_name, email from user where id = 2 union select id, user_name, email from user where id = 4;\n+----+-----------+-----------------+\n| id | user_name | email           |\n+----+-----------+-----------------+\n|  2 | \u4f59\u897f\u5b89     | yusian@163.com  |\n|  4 | Rose      | rose@yusian.com |\n+----+-----------+-----------------+\n2 rows in set (0.00 sec)\n<\/code><\/pre>\n<\/li>\n<li>union\u8fde\u63a5\u7684\u524d\u540e\u67e5\u8be2\u4e2d\uff0c\u67e5\u8be2\u5b57\u6bb5\u6570\u76ee\u8981\u4fdd\u6301\u4e00\u81f4<\/li>\n<\/ul>\n<h3>10\u3001\u5b50\u67e5\u8be2<\/h3>\n<ul>\n<li>\u5c06\u4e00\u4e2a\u67e5\u8be2\u7ed3\u679c\u505a\u4e3a\u53e6\u5916\u4e00\u4e2a\u67e5\u8be2\u7684\u6761\u4ef6\uff1b<\/li>\n<li>where xxx in (select \u2026..)\uff0cmark\u4e2d\u6ca1\u6709id\u4e3a3\u7684user\u6210\u7ee9\uff0c\u56e0\u6b64\u67e5\u8be2\u51fa\u6765\u7684\u7ed3\u679c\u5c31\u662f\u8fd9\u6837\u7684\n<pre><code class=\"language-sql line-numbers\">mysql&gt; select * from user where id in (select user_id from mark);\n+----+-----------+-----+----------------------------------+-----------------+---------+---------+-----+---------------------+\n| id | user_name | sex | password                         | email           | address | fee     | age | create_at           |\n+----+-----------+-----+----------------------------------+-----------------+---------+---------+-----+---------------------+\n|  1 | sian      | \u7537  | e10adc3949ba59abbe56e057f20f883e | yusian@163.com  | NULL    | 1200.31 |  32 | 2019-04-21 20:31:17 |\n|  2 | \u4f59\u897f\u5b89     | \u7537  | c4ca4238a0b923820dcc509a6f75849b | yusian@163.com  | NULL    |    1.00 |  33 | 2019-04-21 17:12:55 |\n|  4 | Rose      | \u5973  | eccbc87e4b5ce2fe28308fd9f2a7baf3 | rose@yusian.com | NULL    |    0.00 |  18 | 2019-04-22 10:46:41 |\n|  5 | Sim       | \u5973  | a87ff679a2f3e71d9181a67b7542122c | sim@yusian.com  | NULL    |    0.00 |  28 | 2019-04-22 10:46:41 |\n|  6 | Tony      | \u7537  | c4ca4238a0b923820dcc509a6f75849b | tony@yusian.com | NULL    |    0.00 |  22 | 2019-04-21 20:41:26 |\n+----+-----------+-----+----------------------------------+-----------------+---------+---------+-----+---------------------+\n5 rows in set (0.00 sec)\n<\/code><\/pre>\n<\/li>\n<\/ul>\n<h3>11\u3001\u67e5\u770b\u5f53\u524d\u5e93\u4e2d\u7684\u8868<\/h3>\n<ul>\n<li>show table status<\/li>\n<li>show table status\\G  \/\/ \u6309\u5217\u663e\u793a<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>DQL: Database Query Language 1\u3001\u67e5\u8be2\u67d0\u5b57\u6bb5\u53bb\u91cd\u590d select distinct xxxx from xxxx 2\u3001\u5408\u5e76\u5b57\u6bb5\u67e5\u8be2\u51fd\u6570concat( )\u3001concat_ws( ) select concat(user_name, password) from user; select concat(user_name, password) as user_name_email from user; select concat_ws(\u2018->\u2019, user_name, password) from user; \/\/ \u67e5\u8be2\u7ed3\u679c\u7528\u2019->\u2019\u5206\u9694\u7b26\u9694\u5f00<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[282],"tags":[327,328,22],"class_list":["post-1899","post","type-post","status-publish","format-standard","hentry","category-database","tag-database","tag-dql","tag-mysql"],"_links":{"self":[{"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/posts\/1899","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/comments?post=1899"}],"version-history":[{"count":0,"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/posts\/1899\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/media?parent=1899"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/categories?post=1899"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.yusian.com\/blog\/wp-json\/wp\/v2\/tags?post=1899"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}