选择不同的 WHERE 条件答案

【问题标题】：SELECT with Different WHERE Conditions选择不同的 WHERE 条件
【发布时间】：2012-07-29 13:28:03
【问题描述】：

我想运行一个这样的选择。

SELECT
        COUNT(*) WHERE switch=0 AND detail=1 AS zeroone
    AND
        COUNT(*) WHERE switch=0 AND detail=2 AS zerotwo
    AND
        COUNT(*) WHERE switch=1 AND detail=1 AS oneone
    AND 
        COUNT(*) WHERE swithc=1 AND detail=2 AS onetwo
  FROM tablename

有没有办法做到这一点？

【问题讨论】：

标签： sql select where

【解决方案1】：

你为什么不用这个？

SELECT COUNT(*) 
  FROM tablename
 GROUP BY switch, detail

【讨论】：

【解决方案2】：

不清楚你想要什么。

我想你想要一个选择，它返回一行，有 4 列：

SELECT
COUNT(*) WHERE switch=0 AND detail=1 AS zeroone,
COUNT(*) WHERE switch=0 AND detail=2 AS zerotwo,
COUNT(*) WHERE switch=1 AND detail=1 AS oneone,
COUNT(*) WHERE swithc=1 AND detail=2 AS onetwo
FROM tablename

【讨论】：

【解决方案3】：

您可以在SELECT 中使用CASE 语句来获取结果：

SELECT SUM(case when switch=0 AND detail=1 then 1 else 0 end) as zeroone
    , SUM(case when switch=0 AND detail=2 then 1 else 0 end) as zerotwo
    , SUM(case when switch=1 AND detail=1 then 1 else 0 end) as oneone
    , SUM(case when switch=1 AND detail=2 then 1 else 0 end) as onetw
FROM tablename

【讨论】：

【解决方案4】：

SELECT
    sum(switch=0 AND detail=1) AS zeroone,
    sum(switch=0 AND detail=2) AS zerotwo,
    sum(switch=1 AND detail=1) AS oneone,
    sum(switch=1 AND detail=2) AS onetwo
FROM tablename

【讨论】：

【解决方案5】：

SELECT SUM(CASE WHEN switch = 0 and detail = 1 THEN 1 ELSE NULL END) AS zeroone
     , ...
FROM TableName

【讨论】：