mysql查询语句

select 字段1，字段2 from 表1，表2 where 字段 group by 分组字段 having 字段 order by 字段  ASC|DESC  limit m,n 

一、查询所有

select * from student;

select name as 姓名 from student;

select name 姓名 from student;

二、条件查询

1.查询学生id等于1

selet * from student where student_id;

2.查询name字段为null

selet * from student where name is null;

3.查询name字段不为null

select * from student where name is not null;

4.查询name字段为空字符串

select * from student where name ='';

5.查询name字段不为空字符串且不为null

select * from student where name !='';

6.查询city字段存在河南省和山东省的数据

select * from where city in('山东省','河南省');

7.查询age在25到30之间

select * from student where age between 25 and 30;

8.查询age不在20到30之间

select * from student where age not between 20 and 30;

9.查询第一个字是郭的数据

select * from student where name like '郭%';

10查询第一个字是郭的两个字得数据

select * from student where name like '郭_';

11查询存在郭的字得数据

select * from student where name like '%郭%';

三、分组查询

1.分组性别

select sex,count(*) from student group by sex;

2.分组性别前条件查询

select sex,count(*) from student where name !='李白' group by sex;

3.分组性别后条件查询

select sex,count(*) from student group by sex having count(*)>5;

4.查询后分组然后再条件查询

select sex,count(*) from student where name !='李白' group by sex having count(*)>5;

四、排序查询

 1.降序排序

select * from student order by salary desc;

2.降序后再升序排序

 select * from student order by salary desc,bonus asc;

五、聚合函数

count(*)
sum(salary)
avg(salary)
min(salary)
max(salary)

 六、连接查询

1.内连接

mysql> select * from class join student on class.class_id=student.class_id;
+----------+----------+------------+----------+--------+------+--------+
| class_id | caption  | student_id | class_id | name   | sex  | gender |
+----------+----------+------------+----------+--------+------+--------+
|        1 | 三年一班 |          1 |        1 | 巨炮   | m    |      1 |
|        1 | 三年一班 |          2 |        1 | 钢弹   | m    |      1 |
|        2 | 三年二班 |          3 |        2 | 七次郎 | m    |      1 |
|        2 | 三年二班 |          4 |        2 | 米线   | m    |      0 |
|        3 | 三年三班 |          5 |        3 | 辣条   | m    |      0 |
+----------+----------+------------+----------+--------+------+--------+
5 rows in set (0.00 sec)

2.左连接

mysql> select * from class left join student on class.class_id=student.class_id;
+----------+----------+------------+----------+--------+------+--------+
| class_id | caption  | student_id | class_id | name   | sex  | gender |
+----------+----------+------------+----------+--------+------+--------+
|        1 | 三年一班 |          1 |        1 | 巨炮   | m    |      1 |
|        1 | 三年一班 |          2 |        1 | 钢弹   | m    |      1 |
|        2 | 三年二班 |          3 |        2 | 七次郎 | m    |      1 |
|        2 | 三年二班 |          4 |        2 | 米线   | m    |      0 |
|        3 | 三年三班 |          5 |        3 | 辣条   | m    |      0 |
|        4 | 四年级   |       NULL |     NULL | NULL   | NULL |   NULL |
+----------+----------+------------+----------+--------+------+--------+
6 rows in set (0.00 sec)

3.右连接

mysql> select * from class right join student on class.class_id=student.class_id;
+----------+----------+------------+----------+--------+------+--------+
| class_id | caption  | student_id | class_id | name   | sex  | gender |
+----------+----------+------------+----------+--------+------+--------+
|        1 | 三年一班 |          1 |        1 | 巨炮   | m    |      1 |
|        1 | 三年一班 |          2 |        1 | 钢弹   | m    |      1 |
|        2 | 三年二班 |          3 |        2 | 七次郎 | m    |      1 |
|        2 | 三年二班 |          4 |        2 | 米线   | m    |      0 |
|        3 | 三年三班 |          5 |        3 | 辣条   | m    |      0 |
|     NULL | NULL     |         12 |     NULL | NULL   | m    |   NULL |
|     NULL | NULL     |         11 |        5 | 骁龙   | m    |   NULL |
|     NULL | NULL     |         13 |        6 | 梦琳   | w    |   NULL |
+----------+----------+------------+----------+--------+------+--------+
8 rows in set (0.00 sec)

4.自然连接（两张表有相同字段名）

mysql> select * from class natural join student;
+----------+----------+------------+--------+------+--------+
| class_id | caption  | student_id | name   | sex  | gender |
+----------+----------+------------+--------+------+--------+
|        1 | 三年一班 |          1 | 巨炮   | m    |      1 |
|        1 | 三年一班 |          2 | 钢弹   | m    |      1 |
|        2 | 三年二班 |          3 | 七次郎 | m    |      1 |
|        2 | 三年二班 |          4 | 米线   | m    |      0 |
|        3 | 三年三班 |          5 | 辣条   | m    |      0 |
+----------+----------+------------+--------+------+--------+
5 rows in set (0.00 sec)

5.联合查询（表和表的结构相同）

mysql> select * from student union select * from student_1;
+------------+----------+--------+------+--------+
| student_id | class_id | name   | sex  | gender |
+------------+----------+--------+------+--------+
|          1 |        1 | 巨炮   | m    |      1 |
|          2 |        1 | 钢弹   | m    |      1 |
|          3 |        2 | 七次郎 | m    |      1 |
|          4 |        2 | 米线   | m    |      0 |
|          5 |        3 | 辣条   | m    |      0 |
|         12 |     NULL | NULL   | m    |   NULL |
|         11 |        5 | 骁龙   | m    |   NULL |
|         13 |        6 | 梦琳   | w    |   NULL |
|          0 |        1 | 小龙   | m    |   NULL |
+------------+----------+--------+------+--------+
9 rows in set (0.00 sec)

 七、子查询

1.标量子查询

select * from score where number > (select avg(number) from score);

2.列子查询

mysql> select * from student where sex in (select sex from student where sex='m'|| sex='w');
+------------+----------+--------+------+--------+
| student_id | class_id | name   | sex  | gender |
+------------+----------+--------+------+--------+
|          1 |        1 | 巨炮   | m    |      1 |
|          2 |        1 | 钢弹   | m    |      1 |
|          3 |        2 | 七次郎 | m    |      1 |
|          4 |        2 | 米线   | m    |      0 |
|          5 |        3 | 辣条   | m    |      0 |
|         12 |     NULL | NULL   | m    |   NULL |
|         11 |        5 | 骁龙   | m    |   NULL |
|         13 |        6 | 梦琳   | w    |   NULL |
+------------+----------+--------+------+--------+
8 rows in set (0.00 sec)

mysql> select * from student where student_id > any (select student_id from student where name in ('巨炮','钢弹','辣条'));
+------------+----------+--------+------+--------+
| student_id | class_id | name   | sex  | gender |
+------------+----------+--------+------+--------+
|          2 |        1 | 钢弹   | m    |      1 |
|          3 |        2 | 七次郎 | m    |      1 |
|          4 |        2 | 米线   | m    |      0 |
|          5 |        3 | 辣条   | m    |      0 |
|         12 |     NULL | NULL   | m    |   NULL |
|         11 |        5 | 骁龙   | m    |   NULL |
|         13 |        6 | 梦琳   | w    |   NULL |
+------------+----------+--------+------+--------+
7 rows in set (0.00 sec)

mysql> select * from student where student_id > all (select student_id from student where name in ('巨炮','钢弹','辣条'));
+------------+----------+------+------+--------+
| student_id | class_id | name | sex  | gender |
+------------+----------+------+------+--------+
|         12 |     NULL | NULL | m    |   NULL |
|         11 |        5 | 骁龙 | m    |   NULL |
|         13 |        6 | 梦琳 | w    |   NULL |
+------------+----------+------+------+--------+
3 rows in set (0.00 sec)

3.行子查询

select * from student where (student_id,name) = (select student_id,name from student where student_id=1);

4.表子查询

select * from (select * from student) as b where student_id>12;

  八、常用

1.过滤重复

 select distinct * from order_info limit 5;

2.随机读取几条数据

select * from order_info order by rand() limit 5;

 3.主键自增从1000开始

 alter table student auto_increment = 1000;