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mysql多表复杂业务查询(如下)，应该怎样写查询语句？

需要查询A、B两张表：

表A table_a ：涉及到两个字段 a_id , a_date


 | a_id      |    a_date  | ...  | ...  |
| :-------- | --------:  | :--: | :--: |
| 1         | 2014-03-12 | ...  | ...  |
| 2         | 2014-03-15 | ...  | ...  |
| 3         | 2013-08-06 | ...  | ...  |
| 4         | 2013-10-18 | ...  | ...  |
| 5         | 2012-04-15 | ...  | ...  |
| 6         | 2012-06-22 | ...  | ...  |
| ...       | ...        | ...  | ...  |

表B table_b ：涉及到两个字段 b_id , b_category


 | b_id      |  b_category | ...  | ...  |
| :-------- | ----------: | :--: | :--: |
| 1         | tom         | ...  | ...  |
| 2         | jerry       | ...  | ...  |
| 3         | tom         | ...  | ...  |
| 4         | jerry       | ...  | ...  |
| 5         | tom         | ...  | ...  |
| 6         | tom         | ...  | ...  |
| ...       | ...         | ...  | ...  |

需求：
1.从 table_b 查询字段名 b_category 等于 tom 的字段 b_id 的值
2.将查得得值关联到 table_a 查询该 a_id 对应的 a_date 的值
3.对 a_date 截取前4位（年份），然后去重，并且按照倒序排列，输出。

sql 数据库 mysql php

11 years, 3 months ago

就是这里了

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就是这里了 11 years, 3 months ago

Answer 1

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 select distinct substr(a_date,1,4) result_date
from table_a inner join table_b on a_id = b_id
where b_category = "tom"
order by result_date desc

answered 11 years, 3 months ago

俊程Jared

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俊程Jared answered 11 years, 3 months ago

mysql多表复杂业务查询(如下)，应该怎样写查询语句？

就是这里了

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俊程Jared

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