MySQL学习笔记之三排序和过滤

在数据库的使用中排序和过滤也是常常的操做

排序检索数据,关键字order

##1.按照某个列名排序

普通排序
mysql> select * from user;
+----+--------+-----+-----------------------+-----+
| id | name   | age | address               | sex |
+----+--------+-----+-----------------------+-----+
|  1 | 张三   |  20 | 北京海底市南区        |   1 |
|  2 | 李四   |  22 | 北京海底市南区        |   1 |
|  3 | 赵芸   |  32 | 上海市徐汇区          |   2 |
|  4 | 王丽   |  31 | 广州厦门              |   2 |
+----+--------+-----+-----------------------+-----+
4 rows in set (0.00 sec)
按照列名name排序是什么样呢？
mysql> select * from user order by name;
+----+--------+-----+-----------------------+-----+
| id | name   | age | address               | sex |
+----+--------+-----+-----------------------+-----+
|  1 | 张三   |  20 | 北京海底市南区        |   1 |
|  2 | 李四   |  22 | 北京海底市南区        |   1 |
|  4 | 王丽   |  31 | 广州厦门              |   2 |
|  3 | 赵芸   |  32 | 上海市徐汇区          |   2 |
+----+--------+-----+-----------------------+-----+
4 rows in set (0.00 sec)

##2.按照多个列名排序

mysql> select * from user order by name, age;
+----+--------+-----+-----------------------+-----+
| id | name   | age | address               | sex |
+----+--------+-----+-----------------------+-----+
|  1 | 张三   |  20 | 北京海底市南区        |   1 |
|  2 | 李四   |  22 | 北京海底市南区        |   1 |
|  4 | 王丽   |  31 | 广州厦门              |   2 |
|  3 | 赵芸   |  32 | 上海市徐汇区          |   2 |
+----+--------+-----+-----------------------+-----+
4 rows in set (0.00 sec)

##3.指定排序方向，默认为字母(a-z),升序

使用关键字desc,能够改成降序排列
mysql> select * from user order by name desc;
+----+--------+-----+-----------------------+-----+
| id | name   | age | address               | sex |
+----+--------+-----+-----------------------+-----+
|  3 | 赵芸   |  32 | 上海市徐汇区          |   2 |
|  4 | 王丽   |  31 | 广州厦门              |   2 |
|  2 | 李四   |  22 | 北京海底市南区        |   1 |
|  1 | 张三   |  20 | 北京海底市南区        |   1 |
+----+--------+-----+-----------------------+-----+
4 rows in set (0.00 sec)

##4.和limit配合使用，限制检索数据数量

mysql> select * from user order by name limit 3;
+----+--------+-----+-----------------------+-----+
| id | name   | age | address               | sex |
+----+--------+-----+-----------------------+-----+
|  1 | 张三   |  20 | 北京海底市南区        |   1 |
|  2 | 李四   |  22 | 北京海底市南区        |   1 |
|  4 | 王丽   |  31 | 广州厦门              |   2 |
+----+--------+-----+-----------------------+-----+
3 rows in set (0.00 sec)

数据过滤，关键字where

##1.检索某一条记录

mysql> select * from user where id = 2;
+----+--------+-----+-----------------------+-----+
| id | name   | age | address               | sex |
+----+--------+-----+-----------------------+-----+
|  2 | 李四   |  22 | 北京海底市南区        |   1 |
+----+--------+-----+-----------------------+-----+
1 row in set (0.00 sec)

和order by 配合使用
mysql> select * from user where id <4  order by name limit 3;
+----+--------+-----+-----------------------+-----+
| id | name   | age | address               | sex |
+----+--------+-----+-----------------------+-----+
|  1 | 张三   |  20 | 北京海底市南区        |   1 |
|  2 | 李四   |  22 | 北京海底市南区        |   1 |
|  3 | 赵芸   |  32 | 上海市徐汇区          |   2 |
+----+--------+-----+-----------------------+-----+
3 rows in set (0.00 sec)

关于where子句的位置: 在同时使用where和order by子句时候, 咱们应该让order by位于where 子句以后。

##2.范围检索--between

mysql> select * from user where id between 2 and 4;
+----+--------+-----+-----------------------+-----+
| id | name   | age | address               | sex |
+----+--------+-----+-----------------------+-----+
|  2 | 李四   |  22 | 北京海底市南区        |   1 |
|  3 | 赵芸   |  32 | 上海市徐汇区          |   2 |
|  4 | 王丽   |  31 | 广州厦门              |   2 |
+----+--------+-----+-----------------------+-----+
3 rows in set (0.00 sec)

##3.过滤--组合where

mysql> select * from user where id >1 and id < 4;
+----+--------+-----+-----------------------+-----+
| id | name   | age | address               | sex |
+----+--------+-----+-----------------------+-----+
|  2 | 李四   |  22 | 北京海底市南区        |   1 |
|  3 | 赵芸   |  32 | 上海市徐汇区          |   2 |
+----+--------+-----+-----------------------+-----+
2 rows in set (0.00 sec)

4. 数据过滤--or 操做符

mysql> select * from user where id <2 or id >=3;
+----+--------+-----+-----------------------+-----+
| id | name   | age | address               | sex |
+----+--------+-----+-----------------------+-----+
|  1 | 张三   |  20 | 北京海底市南区        |   1 |
|  3 | 赵芸   |  32 | 上海市徐汇区          |   2 |
|  4 | 王丽   |  31 | 广州厦门              |   2 |
+----+--------+-----+-----------------------+-----+
3 rows in set (0.00 sec)

##5.数据过滤--in 操做符

in操做符能够用于指定操做范围，范围内每一个条件均可以进行匹配。
mysql> select * from user where name in ("张三","李四");
+----+--------+-----+-----------------------+-----+
| id | name   | age | address               | sex |
+----+--------+-----+-----------------------+-----+
|  1 | 张三   |  20 | 北京海底市南区        |   1 |
|  2 | 李四   |  22 | 北京海底市南区        |   1 |
+----+--------+-----+-----------------------+-----+
2 rows in set (0.00 sec)

in操做符的优点：
1. 使用长的合法选项清单时候, in操做符比较直观。
2. in操做符计算的次序比较好管理
3. in操做符通常比or操做符效率快
4. in操做符能够包括其余select语句，可以更加动态的建立where子句

##6.数据过滤--not操做符

not操做符只有一个特色, 就是否认它后面的任何条件。
mysql支持not对in, between, exists子句取反。

mysql> select * from user where name not in ("张三","李四");
+----+--------+-----+--------------------+-----+
| id | name   | age | address            | sex |
+----+--------+-----+--------------------+-----+
|  3 | 赵芸   |  32 | 上海市徐汇区       |   2 |
|  4 | 王丽   |  31 | 广州厦门           |   2 |
+----+--------+-----+--------------------+-----+
2 rows in set (0.00 sec)

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