作为附加信息，要在SQL Server中完成同样的事情，您只需要删除查询的“FROM dual”部分。

作为附加信息，要在SQL Server中完成同样的事情，您只需要删除查询的“FROM dual”部分。

如果表(或者至少是一个键列)是相同类型的，那么就先做联合，然后计数。

select count(*) 
  from (select tab1key as key from schema.tab1 
        union all 
        select tab2key as key from schema.tab2
       )

或者把你的语句加上另一个和()。

select sum(amount) from
(
select count(*) amount from schema.tab1 union all select count(*) amount from schema.tab2
)

我很快想到了:

Select (select count(*) from Table1) as Count1, (select count(*) from Table2) as Count2

注意:我在SQL Server中测试了这个，所以从Dual是不必要的(因此存在差异)。

SELECT  (
        SELECT COUNT(*)
        FROM   tab1
        ) AS count1,
        (
        SELECT COUNT(*)
        FROM   tab2
        ) AS count2
FROM    dual

Declare @all int
SET @all = (select COUNT(*) from tab1) + (select count(*) from tab2)
Print @all

or

SELECT (select COUNT(*) from tab1) + (select count(*) from tab2)