三、基础查询——MySQL数据库之关键字distinct(2)

偏执的太偏执、 2023-06-21 08:49 12阅读 0赞

## 三、基础查询——MySQL数据库之关键字distinct(2) ##

### 1.distinct作用 ###

**去重**。

举例：比如aiqiyi这张表。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70][]

### 2.使用distinct关键字对某列去重 ###

**语法：**

select distinct [列名1,列名2,...] from 表名;

**示例1：**

从aiqiyi表中的movie\_type列去重。

select distinct movie_type from aiqiyi;

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 1][]

**示例2：**

从aiqiyi表中的area列去重。

select distinct area from aiqiyi;

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 2][]

### 3.使用distinct关键字对多列去重 ###

将aiqiyi表中的area和movie\_type两列同时去重，保证这两列的结果没有重复的。

【比如有一部电影的area和movie\_type是华语和动画，还有一部电影也是华语和动画，那么后出现的那部电影将被去掉】

select distinct area,movie_type from aiqiyi;

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjgzMDY5Nw_size_16_color_FFFFFF_t_70 4][]

### 4.注意点 ###

1.distinct只能置于开头。

2.常用的distinct还是作用于某一列。

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