数据库中Join的区别

几张图解释它们之间的区别

1、inner join

\1.gif

用法：

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

2、left join

\2.gif

用法：

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

3、right join

\3.gif

用法：

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

4、full outer join

\4.gif

用法：

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

其他注意事项

• laravel 中默认join为inner join

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参考网站

• w3cschool SQL Joins