13518219792
先创创建一个表用于测试
-- 创建数据库 CREATE DATABASE dbname DEFAULT CHARSET utf8 COLLATE utf8_general_ci; -- 创建表 CREATE TABLE `tb` ( `id` int(5) NOT NULL AUTO_INCREMENT, `name` char(15) NOT NULL, `alias` varchar(10) DEFAULT NULL, `email` varchar(30) DEFAULT NULL, `password` varchar(20) NOT NULL, `phone` char(11) DEFAULT '13800138000', PRIMARY KEY (`id`,`name`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;查看插入的数据
mysql> select * from tb; +----+---------+-------+-------------------------+----------+-------------+ | id | name | alias | email | password | phone | +----+---------+-------+-------------------------+----------+-------------+ | 2 | ansheng | NULL | anshengme.com@gmail.com | as | 13800138000 | | 3 | as | NULL | i@anshengme.com | pwd | 13800138000 | | 4 | info | NULL | info@anshengme.com | i | 13800138000 | +----+---------+-------+-------------------------+----------+-------------+ 3 rows in set (0.00 sec)把别的表的数据插入当前表
查看tb_copy表内的内容
mysql> select * from tb_copy; +----+--------+-------+-------+----------+-------------+ | id | name | alias | email | password | phone | +----+--------+-------+-------+----------+-------------+ | 5 | hello | NULL | NULL | 1 | 13800138000 | | 6 | word | NULL | NULL | 2 | 13800138000 | | 7 | python | NULL | NULL | 3 | 13800138000 | +----+--------+-------+-------+----------+-------------+ 3 rows in set (0.00 sec)把tb_copy表内的name,email,password列插入到tb表中
insert into tb (name, email, password) select name,email,password from tb_copy;查询tb内的内容
mysql> select * from tb; +----+---------+-------+-------------------------+----------+-------------+ | id | name | alias | email | password | phone | +----+---------+-------+-------------------------+----------+-------------+ | 2 | ansheng | NULL | anshengme.com@gmail.com | as | 13800138000 | | 3 | as | NULL | i@anshengme.com | pwd | 13800138000 | | 4 | info | NULL | info@anshengme.com | i | 13800138000 | | 5 | hello | NULL | NULL | 1 | 13800138000 | | 6 | word | NULL | NULL | 2 | 13800138000 | | 7 | python | NULL | NULL | 3 | 13800138000 | +----+---------+-------+-------------------------+----------+-------------+ 6 rows in set (0.00 sec)查询的时候指定最后一列的名称
mysql> select id,name as username from tb where id > 4; +----+----------+ | id | username | +----+----------+ | 5 | hello | | 6 | word | | 7 | python | +----+----------+ 3 rows in set (0.00 sec)条件
-- 多条件查询 select * from tb where id>3 and name="hello" and password="1"; -- 查询指定范围 select * from tb where id between 4 and 6; -- 查询括号内存在的数据 select * from tb where id in (4,6); -- 查询括号内不存在的数据 select * from tb where id not in (4,6); -- 以别的表的内容为查询条件 select * from tb where id in (select id from tb_copy);通配符
-- 以p开头的所有（多个字符串） select * from tb where name like "p%"; -- 以p开头的所有（一个字符） select * from tb where name like "p%";限制
-- 前三行数据 select * from tb limit 3; -- 从第2行开始的3行 select * from tb limit 2,3; -- 从第4行开始的5行 select * from tb limit 5 offset 4;排序
-- 根据"name"列从小到大排列 select * from tb order by name asc; -- 根据"name"列从大到小排列 select * from tb order by name desc; -- 根据 “列1” 从大到小排列，如果相同则按列2从小到大排序 select * from 表 order by 列1 desc,列2 asc;分组
select id from tb group by id; select id,name from tb group by id,name; select num,nid from 表 where nid > 10 group by num,nid order nid desc; select num,nid,count(*),sum(score),max(score),min(score) from 表 group by num,nid; select num from 表 group by num having max(id) > 10;特别的：group by 必须在where之后，order by之前
连表
无对应关系则不显示
select A.num, A.name, B.name from A,B where A.nid = B.nid;无对应关系则不显示
select A.num, A.name, B.name from A inner join B on A.nid = B.nid;A表所有显示，如果B中无对应关系，则值为null
select A.num, A.name, B.name from A left join B on A.nid = B.nid;B表所有显示，如果B中无对应关系，则值为null
select A.num, A.name, B.name from A right join B on A.nid = B.nid;组合
组合，自动处理重合
select nickname from A union select name from B;组合，不处理重合
select nickname from A union all select name from B;#Python全栈之路
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