Mysql的COUNT和IF使用

Question

我有MySQL的表結構：

| uid  | itemid 
| ------------------- 
| 1001 | 9999 
| 1001 | 8888 
| 2002 | 8888 
| ...  | ... 

UID和爲itemid不是唯一列。 Bun uid + itemid是獨特的組合。

我需要按itemid計數行。我使用下一個查詢：

SELECT itemid, COUNT(*) 
FROM unlikes 
WHERE itemid IN ('9999', '8888') GROUP BY itemid; 

這個工程！

接下來，我需要知道哪一行有混凝土uid。我用：

SELECT itemid, COUNT(*), IF (uid = '1001', TRUE, FALSE) toggled 
FROM unlikes 
WHERE itemid IN ('9999', '8888') GROUP BY itemid;' 

不工作。如果我有不止一行itemid = 8888，那麼比觸發= FALSE。如果組中的一個有uid = 1001，我需要切換= TRUE;

Answer 1

SELECT itemid, COUNT(*), 
CASE WHEN uid = 1001 THEN TRUE ELSE FALSE end AS toggled 
FROM unlikes 
WHERE itemid IN ('9999', '8888') GROUP BY itemid;