動態WHERE子句

Question

我有選擇分組的例子：

SELECT cod, value, type 
FROM table 
GROUP BY cod, value, type 

我得到的結果：

cod | value | type 
1 | 1000 | A 
1 | 570 | B 
2 | 2000 | A 
3 | 1500 | A 
3 | 200 | B 

但僅cod = 1應從type = A返回值。期望的結果：

cod | value | type 
1 | 1000 | A 
2 | 2000 | A 
3 | 1500 | A 
3 | 200 | B 

我認爲CASE聲明WHERE，但有侷限性，不能正常工作。我怎麼能做到這一點？

WHERE CASE WHEN cod = 1 THEN type = 'A' END 

Answer 1

WHERE Type = CASE WHEN cod = 1 THEN 'A' else Type END 

Answer 2

給你：

SELECT cod, value, type 
FROM table 
WHERE cod != 1 OR type='A' 
GROUP BY cod, value, type 

Answer 3

另一個不錯的選擇 - 不，但最好的方式在這裏一個有用的選項。

SELECT cod, value, type 
FROM table 
GROUP BY cod, value, type 

EXCEPT 

SELECT cod, value, type 
FROM table 
WHERE cod = 1 AND type <> 'A' 
GROUP BY cod, value, type