我如何从两个不同的表(叫他们tab1和tab2)选择计数(*)有作为结果:

Count_1   Count_2
123       456

我试过了:

select count(*) Count_1 from schema.tab1 union all select count(*) Count_2 from schema.tab2

但我所拥有的只有:

Count_1
123
456

当前回答

--============= FIRST WAY (Shows as Multiple Row) ===============
SELECT 'tblProducts' [TableName], COUNT(P.Id) [RowCount] FROM tblProducts P
UNION ALL
SELECT 'tblProductSales' [TableName], COUNT(S.Id) [RowCount] FROM tblProductSales S


--============== SECOND WAY (Shows in a Single Row) =============
SELECT  
(SELECT COUNT(Id) FROM   tblProducts) AS ProductCount,
(SELECT COUNT(Id) FROM   tblProductSales) AS SalesCount

其他回答

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

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。

select (select count(*) from tab1) count_1, (select count(*) from tab2) count_2 from dual;

我的经验是使用SQL Server,但是你能做到:

select (select count(*) from table1) as count1,
  (select count(*) from table2) as count2

在SQL Server我得到的结果,你是后。

select @count = sum(data) from
(
select count(*)  as data from #tempregion
union 
select count(*)  as data from #tempmetro
union
select count(*)  as data from #tempcity
union
select count(*)  as data from #tempzips
) a