mysql链接

1 inner join

取相交的部分

语法:

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

2 left join

根据where条件,选择列,以右边为基准，在选择列中,如果存在则显示,否则为null

语法:

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

3 right join

与2相同

语法:

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

4 full join

左链接+右链接

语法:

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