Question

我有4张桌子：

具有字段ID，RequestId，文本
RequestCategory，包含字段Text，RequestId
RequestOutcome，包含字段ID，RequestId
请求字段RequestId

这是我的查询，只有当＆＃34; Total＆＃34;不是0.我想返回类型＆＃34; Text＆＃34;的所有结果。这是我的疑问：

SELECT
                MAX(RC.Text) AS Text,
                MAX(RP.Text) AS TextPossibility,
                COUNT(*) AS Total
FROM Request R
                JOIN RequestOutcome RO ON R.RequestId = RO.Id
                JOIN RequestPossibility RP ON RO.Id = RP.Id
                JOIN RequestCategory RC ON RP.RequestId = RC.RequestId
GROUP BY RP.Id
ORDER BY 1, 2 ASC

Answer 1

如果您计算特定字段并使用LEFT JOIN，则可以解决此问题。

 SELECT
            MAX(RC.Text) AS Text,
            MAX(RP.Text) AS TextPossibility,
            COUNT(R.RequestId) AS Total
FROM Request R
            LEFT JOIN RequestOutcome RO ON R.RequestId = RO.Id
            JOIN RequestPossibility RP ON RO.Id = RP.Id
            JOIN RequestCategory RC ON RP.RequestId = RC.RequestId
GROUP BY RP.Id
ORDER BY 1, 2 ASC

Answer 2

这就是SQL的工作原理。如果查询中没有返回任何行（COUNT(*) == 0），则根本没有结果。

Answer 3

使用LEFT JOIN：

SELECT
                MAX(RC.Text) AS Text,
                MAX(RP.Text) AS TextPossibility,
                COUNT(*) AS Total
FROM Request R
                LEFT JOIN RequestOutcome RO ON R.RequestId = RO.Id
                LEFT JOIN RequestPossibility RP ON RO.Id = RP.Id
                LEFT JOIN RequestCategory RC ON RP.RequestId = RC.RequestId
GROUP BY RP.Id
ORDER BY 1, 2 ASC

编辑＃1：

您的问题中没有指明：＆＃34; 我需要RequestPossibility.Text中的所有结果，无论其他任何表＆＃34;都要返回。检查新查询：

SELECT
                RP.Text AS TextPossibility,
                MAX(RC.Text) AS Text,
                COUNT(*) AS Total
FROM RequestPossibility RP
                LEFT JOIN Request R ON R.RequestId = RP.RequestId
                LEFT JOIN RequestOutcome RO ON RP.RequestId = RO.Id
                LEFT JOIN RequestCategory RC ON RP.RequestId = RC.RequestId
GROUP BY RP.Text
ORDER BY 1, 2 ASC

Answer 4

使用左/右连接时，表的顺序会有所不同。试试这个：

SELECT MAX(RC.Text) AS Text, 
MAX(RP.Text) AS TextPossibility, 
COUNT(*) AS Total 
FROM RequestPossibility RP 
LEFT JOIN Request R ON RP.id = R.RequestId
LEFT JOIN RequestOutcome RO ON R.RequestId = RO.Id 
LEFT JOIN RequestCategory RC ON RP.RequestId = RC.RequestId 
GROUP BY RP.Id 
ORDER BY 1, 2 ASC

Answer 5

你需要离开，你需要按R.RequestId（最左边）

进行分组

SELECT  R.RequestId,
        MAX(RC.Text) AS Text,
        MAX(RP.Text) AS TextPossibility,
        COUNT(*) AS Total
FROM Request R
Left JOIN RequestOutcome RO 
  ON R.RequestId = RO.Id
left JOIN RequestPossibility RP 
  ON R.RequestId = RP.Id
left JOIN RequestCategory RC 
  ON RP.RequestId = RC.RequestId
GROUP BY R.RequestId
ORDER BY 2, 3 ASC

你在最后一次加入时翻到RequestId很奇怪 RequestId没有链接到R.RequestId

你想要RequestPossibility.Text中的所有结果然后基本查询离开了我不清楚你真正想要的是什么

   SELECT  RP.Text AS TextPossibility
           MAX(RC.Text) AS Text,
           COUNT(*) AS Total
    RequestPossibility RP        
    left join Request R
      ON R.RequestId = RP.Id
    Left JOIN RequestOutcome RO 
      ON RP.Id = RO.Id
    left JOIN RequestCategory RC 
      ON RP.RequestId = RC.RequestId
    GROUP BY RP.Text
    ORDER BY 1, 2 ASC

Answer 6

SELECT
                MAX(RC.Text) AS Text
,               MAX(RP.Text) AS TextPossibility
,               COUNT(R.RequestId) AS Total
FROM Request R
                LEFT JOIN RequestOutcome RO ON R.RequestId = RO.RequestId
                RIGHT OUTER JOIN RequestPossibility RP ON RO.Id = RP.Id
                RIGHT OUTER JOIN RequestCategory RC ON RP.RequestId = RC.RequestId
GROUP BY RP.Id
ORDER BY 1, 2 ASC

如果total为零，则显示所有字段

6 个答案: