SQL连接查询(JOIN)

SQL连接查询(JOIN)

主要列举这个图：

INNER JOIN

SELECT column_name(s)
FROM table1
INNER JOIN table2
ON table1.column_name=table2.column_name;

或者，

SELECT column_name(s)
FROM table1
JOIN table2
ON table1.column_name=table2.column_name;

LEFT JOIN

SELECT column_name(s)
FROM table1
LEFT JOIN table2
ON table1.column_name=table2.column_name;

或者，

SELECT column_name(s)
FROM table1
LEFT OUTER JOIN table2
ON table1.column_name=table2.column_name;

RIGHT JOIN

同理，

SELECT column_name(s)
FROM table1
LEFT JOIN table2
ON table1.column_name=table2.column_name;

或者，

SELECT column_name(s)
FROM table1
LEFT OUTER JOIN table2
ON table1.column_name=table2.column_name;

FULL OUTER JOIN

SELECT column_name(s)
FROM table1
FULL OUTER JOIN table2
ON table1.column_name=table2.column_name;
```![在这里插入图片描述](https://img-blog.csdnimg.cn/20190404134555374.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3hpYWJlbnNodQ==,size_16,color_FFFFFF,t_70)

# 简单举个left join的例子
表1：
![在这里插入图片描述](https://img-blog.csdnimg.cn/20190404134727702.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3hpYWJlbnNodQ==,size_16,color_FFFFFF,t_70)
表2：
![在这里插入图片描述](https://img-blog.csdnimg.cn/20190404134739446.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3hpYWJlbnNodQ==,size_16,color_FFFFFF,t_70)
查询结果，
![在这里插入图片描述](https://img-blog.csdnimg.cn/20190404134807685.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3hpYWJlbnNodQ==,size_16,color_FFFFFF,t_70)