SQL Server 子查询不返回任何记录 [英] SQL Server Subquery Returning No Records

问题描述

我有一个非常简单的子查询:

I have what should be a very simple subquery:

DECLARE @count TABLE (count1 INT, count2 INT)

SELECT
    (SELECT COUNT(*) FROM Bird) AS count1,
    (SELECT COUNT(*) FROM Fish) AS count2
FROM @count

• 当我运行 SELECT COUNT(*) FROM Bird 时，我得到了 10.
• 当我运行 SELECT COUNT(*) FROM Fish 时，我得到 5 个返回值.
• 运行上述查询时，返回的记录为零.
• When I run SELECT COUNT(*) FROM Bird I get 10 back.
• When I run SELECT COUNT(*) FROM Fish I get 5 returned.
• When I run the above query, I get zero records returned.

我错过了什么吗?我看过多个不同的教程，他们都说要做我正在做的事情.

Am I missing something? I've seen multiple different tutorials and they all say to do pretty much exactly what I am doing.

推荐答案

我假设您正在尝试将两个计数插入到您声明的表中.如果这是真的，您将缺少 INSERT INTO 并且有一个 FROM @count 您不需要...

I assume, that you are trying to insert the two counts into your declared table. If this is true you are missing an INSERT INTO and there is one FROM @count you don't need...

在本例中，我使用两个计数(在其他表上)将一行插入到 @count 中，您可以在最后一步中选择:

In this example I use two count (on other tables) to insert one row into @count, which you can select in the last step:

declare @count table (count1 int, count2 int);

INSERT INTO @count
select (SELECT COUNT(*) FROM sys.all_columns)
      ,(SELECT COUNT(*) FROM sys.tables);

SELECT * FROM @count;

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