---
notion-id: 850ec1a5-5504-460c-91b3-8aa88ddccc37
---

![[IMG-20260516155654659.png]]
# 7中JOIN的实现
```plain text
左连接
Select <select_list>
FROM table A
LEFT JOIN table B
ON A.KEY = B.KEY
```
```plain text
右连接
Select <select_list>
FROM table A
RIGHT JOIN table B
ON A.KEY = B.KEY
```
```plain text
内连接
Select <select_list>
FROM table A
INNER JOIN table B
ON A.KEY = B.KEY
```
```plain text
左连接【去除右表数据】
Select <select_list>
FROM table A
LEFT JOIN table B
ON A.KEY = B.KEY
Where B.KEY IS NULL
```
```plain text
右连接【去除左表数据】
Select <select_list>
FROM table A
RIGHT JOIN table B
ON A.KEY = B.KEY
Where A.KEY IS NULL
```
```sql
#满内连接【mysql不支持】 可使用左连接+右连接【去除左表数据】 UNION ALL 右连接+左连接【去除右表数据】
Select <select_list>
FROM table A
FULL JOIN table B
ON A.KEY = B.KEY

#可使用UNION ALL来拼接
Select <select_list>
FROM table A
LEFT JOIN table B
ON A.KEY = B.KEY
UNION ALL
Select <select_list>
FROM table A
RIGHT JOIN table B
ON A.KEY = B.KEY
Where A.KEY IS NULL;


```
```sql
#满外连接【mysql不支持】 可使用左连接【去除右表数据】 UNION ALL右连接【去除左表数据】实现
Select <select_list>
FROM table A
FULL OUTER JOIN table B
ON A.KEY = B.KEY
WHERE A.KEY IS NULL
OR B.KEY IS NULL

#使用UNION ALL拼接

```