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马哥linux运维学习笔记-MySQL系列之七——单表查询、多表查询和子查询
发布时间：2019-03-15 17:50:46编辑：雪饮阅读（）
查询结果指定某个字段去重
正常查询
mysql> select money from s_user where money>0;
+-------+
| money |
+-------+
| 1 |
| 1 |
+-------+
去重查询
mysql> select distinct money from s_user where money>0;
+-------+
| money |
+-------+
| 1 |
+-------+
1 row in set (0.00 sec)
模糊查询
以某字符开头，剩下字符并不知道，只知道剩下字符个数
mysql> select username from s_user where username like '温__';
+-----------+
| username |
+-----------+
| 温晓艺 |
+-----------+
1 row in set (0.00 sec)
模糊查询-正则
查询以x或s或p开头的用户名
mysql> select username from s_user where username rlike '^[xsp].*';
+--------------+
| username |
+--------------+
| Sunny |
| sissi |
| park |
| Smile丶 |
| Shawn |
| Perry |
| sunrise |
| Pink Gorilla |
| Shaw |
| Pancato |
| Peterpan |
| xygg |
| Portrait |
| puqiong |
+--------------+
14 rows in set (0.00 sec)
数学计算
mysql> select 2+1;
+-----+
| 2+1 |
+-----+
| 3 |
+-----+
1 row in set (0.00 sec)
mysql> select 2+1 as sum;
+-----+
| sum |
+-----+
| 3 |
+-----+
1 row in set (0.00 sec)
查询结果分组后的进一步筛选
查询结果通过group by进行聚合运算后若还要进行进一步筛选就要用having
mysql> select count(*),sex from s_user group by sex having sex='女士';
+----------+--------+
| count(*) | sex |
+----------+--------+
| 60 | 女士 |
+----------+--------+
1 row in set (0.00 sec)
关键字词：linux,mysql