三篇学会MySQL数据库查询详解

Posted 2022-05-27 周棋洛ყ ᥱ ᥉

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作者：周棋洛
上篇：三篇学会MySQL数据库，第一篇
简介：mysql万字教程，从入门到精通，第二篇查询，第三篇讲讲解视图，存储过程，触发器，事物，维护，备份恢复等高级知识，单独写一篇是因为查询使用频率太高，一万五千字，放上完美无水印脑图，方便下载后期复习，原创不易，一键三联，多多支持呀！⛽

文章目录

无水印脑图
表结构
简单查询
模糊查询
排序查询
聚合函数
分组查询
select子句查询顺序
分页查询
多表查询

无水印脑图

表结构

mysql> desc stus;
+---------+--------------+------+-----+---------+----------------+
| Field   | Type         | Null | Key | Default | Extra          |
+---------+--------------+------+-----+---------+----------------+
| id      | int(11)      | NO   | PRI | NULL    | auto_increment |
| gradeId | int(11)      | YES  | MUL | NULL    |                |
| NAME    | varchar(100) | NO   |     | NULL    |                |
| age     | int(3)       | YES  |     | NULL    |                |
| bir     | date         | YES  |     | NULL    |                |
| english | int(3)       | YES  |     | NULL    |                |
| chinese | int(3)       | YES  |     | NULL    |                |
+---------+--------------+------+-----+---------+----------------+

mysql> select * from stus;
+----+---------+--------------+------+------------+---------+---------+
| id | gradeId | NAME         | age  | bir        | english | chinese |
+----+---------+--------------+------+------------+---------+---------+
|  1 |       1 | 周棋洛       |   18 | 2001-06-01 |      78 |    NULL |
|  2 |       2 | 张郁苗       |   18 | 2002-11-07 |     130 |     120 |
|  3 |       1 | 小猪佩奇     |    6 | 2015-06-10 |      34 |    NULL |
|  4 |       3 | 猪爸爸       |    8 | 2012-09-12 |      34 |      56 |
|  5 |       3 | 猪妈妈       |    7 | 2012-09-11 |      56 |      78 |
+----+---------+--------------+------+------------+---------+---------+

简单查询

脑图

单列查询

select 列名 from 表;

从stus表中查询名字的字段

mysql> select name from stus;
+--------------+
| name         |
+--------------+
| 周棋洛       |
| 张郁苗       |
| 小猪佩奇     |
| 猪爸爸       |
| 猪妈妈       |
+--------------+

查询多列

select 列名,列名…… from 表;

从stus表中查询名字和年龄这两个字段

mysql> select name,age from stus;
+--------------+------+
| name         | age  |
+--------------+------+
| 周棋洛       |   18 |
| 张郁苗       |   18 |
| 小猪佩奇     |    6 |
| 猪爸爸       |    8 |
| 猪妈妈       |    7 |
+--------------+------+

查询所有列 *

select * from 表;

从stus表查询所有字段

mysql> select * from stus;
+----+---------+--------------+------+------------+---------+---------+
| id | gradeId | NAME         | age  | bir        | english | chinese |
+----+---------+--------------+------+------------+---------+---------+
|  1 |       1 | 周棋洛       |   18 | 2001-06-01 |      78 |    NULL |
|  2 |       2 | 张郁苗       |   18 | 2002-11-07 |     130 |     120 |
|  3 |       1 | 小猪佩奇     |    6 | 2015-06-10 |      34 |    NULL |
|  4 |       3 | 猪爸爸       |    8 | 2012-09-12 |      34 |      56 |
|  5 |       3 | 猪妈妈       |    7 | 2012-09-11 |      56 |      78 |
+----+---------+--------------+------+------------+---------+---------+

distinct去重

distinct关键字可以出去重复出现的内容，注意：不能部分使用distinct

mysql> select distinct age from stus;
+------+
| age  |
+------+
|   18 |
|    6 |
|    8 |
|    7 |
+------+

起别名 as

我们在查询时，如果对原有字段名不满意，这时就可以通过as关键字对字段起别名，注意：as是可省略的，如下所示

mysql> select name as "姓名" from stus;
+--------------+
| 姓名         |
+--------------+
| 周棋洛       |
| 张郁苗       |
| 小猪佩奇     |
| 猪爸爸       |
| 猪妈妈       |
+--------------+

mysql> select name "姓名" from stus;
+--------------+
| 姓名         |
+--------------+
| 周棋洛       |
| 张郁苗       |
| 小猪佩奇     |
| 猪爸爸       |
| 猪妈妈       |
+--------------+

条件查询

大于判断 >

😀 : 查找stus表中年龄大于18岁的学生姓名

mysql> select name from stus where age > 18;
Empty set (0.00 sec)

小于判断 <

😀 : 查找stus表中年龄小于18岁的学生姓名

mysql> select name from stus where age < 18;
+--------------+
| name         |
+--------------+
| 小猪佩奇     |
| 猪爸爸       |
| 猪妈妈       |
+--------------+

等于判断 =

😀 : 查找stus表中年龄等于18岁的学生姓名

mysql> select name from stus where age = 18;
+-----------+
| name      |
+-----------+
| 周棋洛    |
| 张郁苗    |
+-----------+

大于等于判断 >=

😀 : 查找stus表中年龄大于等于18岁的学生姓名

mysql> select name from stus where age >= 18;
+-----------+
| name      |
+-----------+
| 周棋洛    |
| 张郁苗    |
+-----------+

小于等于判断 <=

😀 : 查找stus表中年龄小于等于18岁的学生姓名

mysql> select name from stus where age <= 18;
+--------------+
| name         |
+--------------+
| 周棋洛       |
| 张郁苗       |
| 小猪佩奇     |
| 猪爸爸       |
| 猪妈妈       |
+--------------+

不等于判断 <> 或 !=

😀 : 查找stus表中年龄不等于18岁的学生姓名

mysql> select name from stus where age <> 18;
+--------------+
| name         |
+--------------+
| 小猪佩奇     |
| 猪爸爸       |
| 猪妈妈       |
+--------------+

mysql> select name from stus where age != 18;
+--------------+
| name         |
+--------------+
| 小猪佩奇     |
| 猪爸爸       |
| 猪妈妈       |
+--------------+

BETWEEN … AND …包含判断

😀 : 查找stus表中年龄在10~18岁的学生姓名

mysql> select name,age from stus where age between 8 and 20;
+-----------+------+
| name      | age  |
+-----------+------+
| 周棋洛    |   18 |
| 张郁苗    |   18 |
| 猪爸爸    |    8 |
+-----------+------+

IN(…)

😀 : 查找stus表中年龄为8岁或7岁的学生姓名

mysql> select name,age from stus where age in(7,8);
+-----------+------+
| name      | age  |
+-----------+------+
| 猪爸爸    |    8 |
| 猪妈妈    |    7 |
+-----------+------+

IS NULL

😀 : 查找stus表中名字为空的学生信息

mysql> select * from stus where name is null;
Empty set (0.02 sec)

IS NOT NULL

😀 : 查找stus表中名字不为空的学生信息

mysql> select * from stus where name is not null;
+----+---------+--------------+------+------------+---------+---------+
| id | gradeId | NAME         | age  | bir        | english | chinese |
+----+---------+--------------+------+------------+---------+---------+
|  1 |       1 | 周棋洛       |   18 | 2001-06-01 |      78 |    NULL |
|  2 |       2 | 张郁苗       |   18 | 2002-11-07 |     130 |     120 |
|  3 |       1 | 小猪佩奇     |    6 | 2015-06-10 |      34 |    NULL |
|  4 |       3 | 猪爸爸       |    8 | 2012-09-12 |      34 |      56 |
|  5 |       3 | 猪妈妈       |    7 | 2012-09-11 |      56 |      78 |
+----+---------+--------------+------+------------+---------+---------+

AND 或 &&

只有多个条件都成立才会返回真，否则就认为false

😀 : 查找stus表中年龄为18岁的周棋洛的学生信息

mysql> select * from stus where name = "周棋洛" AND age = "18";
+----+---------+-----------+------+------------+---------+---------+
| id | gradeId | NAME      | age  | bir        | english | chinese |
+----+---------+-----------+------+------------+---------+---------+
|  1 |       1 | 周棋洛    |   18 | 2001-06-01 |      78 |    NULL |
+----+---------+-----------+------+------------+---------+---------+

mysql> select * from stus where name = "周棋洛" && age = "18";
+----+---------+-----------+------+------------+---------+---------+
| id | gradeId | NAME      | age  | bir        | english | chinese |
+----+---------+-----------+------+------------+---------+---------+
|  1 |       1 | 周棋洛    |   18 | 2001-06-01 |      78 |    NULL |
+----+---------+-----------+------+------------+---------+---------+

OR 或 ||

只要有一个条件成立就返回真，都不成立返回false

😀 : 查找stus表中名字叫周棋洛或者叫张郁苗的学生信息

mysql> select * from stus where name = "周棋洛" OR name = "张郁苗";
+----+---------+-----------+------+------------+---------+---------+
| id | gradeId | NAME      | age  | bir        | english | chinese |
+----+---------+-----------+------+------------+---------+---------+
|  1 |       1 | 周棋洛    |   18 | 2001-06-01 |      78 |    NULL |
|  2 |       2 | 张郁苗    |   18 | 2002-11-07 |     130 |     120 |
+----+---------+-----------+------+------------+---------+---------+

mysql> select * from stus where name = "周棋洛" || name = "张郁苗";
+----+---------+-----------+------+------------+---------+---------+
| id | gradeId | NAME      | age  | bir        | english | chinese |
+----+---------+-----------+------+------------+---------+---------+
|  1 |       1 | 周棋洛    |   18 | 2001-06-01 |      78 |    NULL |
|  2 |       2 | 张郁苗    |   18 | 2002-11-07 |     130 |     120 |
+----+---------+-----------+------+------------+---------+---------+

模糊查询

糊查询 需要使用 like 占位符，几个案例学会模糊查询，下面是stus表的数据

脑图

mysql> select * from stus;
+----+---------+--------------+------+------------+---------+---------+
| id | gradeId | NAME         | age  | bir        | english | chinese |
+----+---------+--------------+------+------------+---------+---------+
|  1 |       1 | 周棋洛       |   18 | 2001-06-01 |      78 |    NULL |
|  2 |       2 | 张郁苗       |   18 | 2002-11-07 |     130 |     120 |
|  3 |       1 | 小猪佩奇     |    6 | 2015-06-10 |      34 |    NULL |
|  4 |       3 | 猪爸爸       |    8 | 2012-09-12 |      34 |      56 |
|  5 |       3 | 猪妈妈       |    7 | 2012-09-11 |      56 |      78 |
+----+---------+--------------+------+------------+---------+---------+

% 多个任意字符

1.查询 stus 表中 name 以猪开头的学生信息

mysql> select * from stus where name like "猪%";
+----+---------+-----------+------+------------+---------+---------+
| id | gradeId | NAME      | age  | bir        | english | chinese |
+----+---------+-----------+------+------------+---------+---------+
|  4 |       3 | 猪爸爸    |    8 | 2012-09-12 |      34 |      56 |
|  5 |       3 | 猪妈妈    |    7 | 2012-09-11 |      56 |      78 |
+----+---------+-----------+------+------------+---------+---------+

2.查询 stus 表中 name 以爸爸结尾的学生信息

mysql> select * from stus where name like '%爸爸';
+----+---------+-----------+------+------------+---------+---------+
| id | gradeId | NAME      | age  | bir        | english | chinese |
+----+---------+-----------+------+------------+---------+---------+
|  4 |       3 | 猪爸爸    |    8 | 2012-09-12 |      34 |      56 |
+----+---------+-----------+------+------------+---------+---------+

3.查询 stus 表中 name 中包含猪的学生信息

mysql> select * from stus where name like '%猪%';
+----+---------+--------------+------+------------+---------+---------+
| id | gradeId | NAME         | age  | bir        | english | chinese |
+----+---------+--------------+------+------------+---------+---------+
|  3 |       1 | 小猪佩奇     |    6 | 2015-06-10 |      34 |    NULL |
|  4 |       3 | 猪爸爸       |    8 | 2012-09-12 |      34 |      56 |
|  5 |       3 | 猪妈妈       |    7 | 2012-09-11 |      56 |      78 |
+----+---------+--------------+------+------------+---------+---------+

_ 单个任意字符

4.查询 stus 表中 name 以猪开头的且名字长度为2的学生信息

mysql> select * from stus where name like '猪_';
Empty set (0.00 sec)

5.查询 stus 表中 name 以猪开头的且名字长度为3的学生信息

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