选择一些不同的列

Question

这是一些测试数据。

+----+------+-------+---------+---------+ 
| id | type | param | enabled | account | 
+----+------+-------+---------+---------+ 
| 1 | test |  a |  1 | null | 
| 2 | asdf |  b |  1 | null | 
| 3 | test |  c |  1 |  34 | 
| 4 | test |  d |  0 |  34 | 
| 5 | asdf |  e |  1 | null | 
+----+------+-------+---------+---------+ 

我想选择最新的行，其中“类型”和“帐户”是唯一的。

例如，对于测试表，我想要的结果：

+----+------+-------+---------+---------+ 
| id | type | param | enabled | account | 
+----+------+-------+---------+---------+ 
| 1 | test |  a |  1 | null | 
| 4 | test |  d |  0 |  34 | 
| 5 | asdf |  e |  1 | null | 
+----+------+-------+---------+---------+ 

我试着按组的变化：

SELECT * FROM test GROUP BY type, account 

出于某种原因，让我这样的：

+----+------+-------+---------+---------+ 
| id | type | param | enabled | account | 
+----+------+-------+---------+---------+ 
| 1 | test |  a |  1 | null | 
| 4 | test |  d |  1 |  34 | <- note that enabled is taking on an incorrect value. 
| 5 | asdf |  e |  1 | null | 
+----+------+-------+---------+---------+ 

什么是正确的方法来做到这一点？

Answer 1

如果您的查询是给你正确的ID，你应该尝试把它变成一个子查询：

SELECT * FROM test WHERE id IN (SELECT id FROM test GROUP BY type, account) 

Answer 2

假设“最新行”是指具有最大id，那么有几种方法。使用in的方法是：

SELECT t.* 
FROM test t 
WHERE t.id IN (SELECT MAX(id) FROM test t2 GROUP BY type, account)