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

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)。

其他回答

为了完整起见,这个查询将创建一个查询,为您提供给定所有者的所有表的计数。

select 
  DECODE(rownum, 1, '', ' UNION ALL ') || 
  'SELECT ''' || table_name || ''' AS TABLE_NAME, COUNT(*) ' ||
  ' FROM ' || table_name  as query_string 
 from all_tables 
where owner = :owner;

输出是这样的

SELECT 'TAB1' AS TABLE_NAME, COUNT(*) FROM TAB1
 UNION ALL SELECT 'TAB2' AS TABLE_NAME, COUNT(*) FROM TAB2
 UNION ALL SELECT 'TAB3' AS TABLE_NAME, COUNT(*) FROM TAB3
 UNION ALL SELECT 'TAB4' AS TABLE_NAME, COUNT(*) FROM TAB4

然后你可以运行它来得到你的计数。有时它只是一个方便的脚本。

选择 (select count() from tab1 where field like 'value') + (select count() from tab2 where field like 'value') 数

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
--============= 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
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)