Mysql的COUNT和IF使用

Question

我有MySQL的表结构：

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

UID和为itemid不是唯一列。 Bun uid + itemid是独特的组合。

我需要按itemid计数行。我使用下一个查询：

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

这个工程！

接下来，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，那么比触发= FALSE。如果组中的一个有uid = 1001，我需要切换= 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;