在SQL查询合并中需要帮助

本文介绍了在SQL查询合并中需要帮助的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

大家好 如何合并这些查询

Hi all How to merge these query

select count(a.pk_id) from test a union select count(b.pk_id) from usertesting b union select count(c.user_id) from user1 c;

意味着要在单个查询中编写 我尝试了

means wants to write in single query i tried

select count(a.pk_id),count(b.pk_id),count(c.user_id) from test a ,usertesting b, user1 c;

但这并未显示出真实的结果，因此还尝试使用其他联接. 无法在单个查询中编写上述查询 请帮助我在单个查询中编写以上查询 在此先感谢您.

but this is not showing the true result and also tried using different joining. Unable to write this above query in a single query Please help me to write the above query in a single query Thanks in advance.

推荐答案

第二个查询未显示真实结果的原因是因为您联接的表没有任何链接.这意味着计数将与其他表相乘.测试*用户测试*用户1. 因此，如果您有以下表格: The reason your second query is not showing a true result is because you''re joining the tables without any kind on link. That means that the counts will be multiplied by the other tables. test * usertesting * user1. So if you had the following tables: TableA, TableB, TableC 1 6 a 2 7 b 3 8 c

通过像在第二个查询中一样进行选择，您将获得以下结果:

By selecting as you do in the second query you''d get the following results:

AValue, BValue, CValue 1 6 a 1 6 b 1 6 c 1 7 a 1 7 b 1 7 c 1 8 a 1 8 b 1 8 c 2 6 a 2 6 b 2 6 c 2 7 a 2 7 b 2 7 c 2 8 a 2 8 b 2 8 c 3 6 a 3 6 b 3 6 c 3 7 a 3 7 b 3 7 c 3 8 a 3 8 b 3 8 c

我个人认为，联合选择是获取所需数据的最佳方法，但以下方法应该可以达到您想要的结果.

Personally I think the union select is the best way to get the data you''re after but the following should achieve your desired result.

SELECT cTest, cUserTesting, cUser1 FROM (SELECT cTest = COUNT(pk_id) FROM test), (SELECT cUserTesting = COUNT(pk_id) FROM usertesting), (SELECT cUser1 = COUNT(user_id) FROM user1)

由于列出的每个表只有一行，因此结果不会相乘. 虽然如果您遇到工会问题，则不知道哪个计数可以尝试以下操作.

As each of the tables listed only has one row there won''t be a multiplication of results. Although if your problem with the union is you don''t know which count is which you could try the following.

select cType = 'test', vCount = count(a.pk_id) from test a union select 'usertesting', count(b.pk_id) from usertesting b union select 'user1', count(c.user_id) from user1 c;

，您可以通过以下方式使用变量: You can do it in this way, using variables: DECLARE @c1 INT DECLARE @c2 INT DECLARE @c3 INT select @c1 = count(a.pk_id) from test a select @c2 = count(b.pk_id) from usertesting b select @c3 = count(c.user_id) from user1 c; SELECT @c1 AS [aPk_id], @c2 AS [bPk_id], @c3 AS [cUs_id]