如何使子查询正确

Question

大家好，我对 SQL 中的子查询有些问题。我正在使用 MS Access 2010 并编写 sql。

SELECT vak.Name, COUNT(vak.amount) AS [First], COUNT(vak2.amount2) AS [Second]    
FROM  
(SELECT kon.Name, (Count(icv.CV_ID) / Count(icv.CV_ID)) AS amount  
 FROM (kon INNER JOIN v ON kon.K_ID = v.K_ID) INNER JOIN icv ON v.Vak_ID = icv.Vak_ID  
 GROUP BY v.Vak_ID, kon.Name) AS vak,  
(SELECT kon.Name, COUNT(v.Vak_ID) AS amount2  
 FROM (kon INNER JOIN v ON kon.K_ID = v.K_ID) INNER JOIN icv ON v.Vak_ID = icv.Vak_ID  
 GROUP BY kon.Name) AS vak2  
GROUP BY vak.Konkursa_Nosaukums

当我在数据表视图中检查它时，两列是相同的。 “第一”中有 6 行，值分别为 12、12、6、12、6、6。“第二”列中的值相同。当我将此代码分成两部分并进行 2 个新查询进行测试时，“第一”列显示值 2、2、1、2、1、1，第二个查询的值为 3、3、1、2、1， 1.这两列分开时都有正确的值，但是当我将它们组合在一起时，一些未知值看起来像 12（我不知道它在哪里取像 12 这样的数字）。当我放线时
WHERE vak.amount=vak2.amount2 在最后一行之前它在两列中显示 2,2,1,2,1,1。我想它只需要第一个子查询或其他东西。

如何正确地制作这些子查询，使它们显示的值与单独编写时相同？

Answer 1

我认为您缺少加入条件，并且在适当的组中...

SELECT vak.Name, vak.amount AS [First], vak2.amount2 AS [Second]
FROM  
(SELECT kon.Name, (Count(icv.CV_ID) / Count(icv.CV_ID)) AS amount  
 FROM (kon INNER JOIN v ON kon.K_ID = v.K_ID) INNER JOIN icv ON v.Vak_ID = icv.Vak_ID  
 GROUP BY v.Vak_ID, kon.Name) AS vak,
(SELECT kon.Name, COUNT(v.Vak_ID) AS amount2  
 FROM (kon INNER JOIN v ON kon.K_ID = v.K_ID) INNER JOIN icv ON v.Vak_ID = icv.Vak_ID  
 GROUP BY kon.Name) AS vak2  
WHERE vak.Name = van2.Name

Answer 2

SELECT vak.Name, vak.amount AS [First], vak2.amount2 AS [Second]
FROM  
(SELECT kon.Name, (Count(icv.CV_ID) / Count(icv.CV_ID)) AS amount  
 FROM (kon INNER JOIN v ON kon.K_ID = v.K_ID) INNER JOIN icv ON v.Vak_ID = icv.Vak_ID  
 GROUP BY v.Vak_ID, kon.Name) AS vak,
(SELECT kon.Name, COUNT(v.Vak_ID) AS amount2  
 FROM (kon INNER JOIN v ON kon.K_ID = v.K_ID) INNER JOIN icv ON v.Vak_ID = icv.Vak_ID  
 GROUP BY kon.Name) AS vak2  
WHERE vak.Name = van2.Name