我有3个表,foo,foo2bar和bar. foo2bar是foo和bar之间的很多地图.这里是内容.
- select * from foo
- +------+
- | fid |
- +------+
- | 1 |
- | 2 |
- | 3 |
- | 4 |
- +------+
- select * from foo2bar
- +------+------+
- | fid | bid |
- +------+------+
- | 1 | 1 |
- | 1 | 2 |
- | 2 | 1 |
- | 2 | 3 |
- | 4 | 4 |
- +------+------+
- select * from bar
- +------+-------+------+
- | bid | value | zid |
- +------+-------+------+
- | 1 | 2 | 10 |
- | 2 | 4 | 20 |
- | 3 | 8 | 30 |
- | 4 | 42 | 30 |
- +------+-------+------+
我想要的是,“给我一个所有的fid和值的列表,带有30”
我期待所有的fids的答案,所以结果将是：
- +------+--------+
- | fid | value |
- +------+--------+
- | 1 | null |
- | 2 | 8 |
- | 3 | null |
- | 4 | 42 |
- +------+--------+
