選擇一些不同的列

Question

這是一些測試數據。

+----+------+-------+---------+---------+ 
| 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 | 
+----+------+-------+---------+---------+ 

我想選擇最新的行，其中「類型」和「帳戶」是唯一的。

例如，對於測試表，我想要的結果：

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

我試着按組的變化：

SELECT * FROM test GROUP BY type, account 

出於某種原因，讓我這樣的：

+----+------+-------+---------+---------+ 
| 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 | 
+----+------+-------+---------+---------+ 

什麼是正確的方法來做到這一點？

Answer 1

如果您的查詢是給你正確的ID，你應該嘗試把它變成一個子查詢：

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

Answer 2

假設「最新行」是指具有最大id，那麼有幾種方法。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)