如何将两个查询的结果合并为一行？

Question

我有两个查询，每个查询返回一个结果，即一个数字

Select Count(*) as StockCountA from Table_A where dept='AAA'

结果

StockCountA 
550

。

Select Count(*) as StockCountB from Table_B where dept='BBB'

结果

StockCountB 
450

我希望将两个结果合并为一行记录，即

| StockCountA | StockCountB    
| 550         | 450

Answer 1

您可以使用：

select
(Select Count(*) as StockCountA from Table_A where dept='AAA') as StockCountA,
(Select Count(*) as StockCountB from Table_B where dept='BBB') as StockCountB

说明：您可以在select语句中选择单个值作为字段，因此可以编写如下内容

select
  x.*,
  (select Value from Table_Y y) as ValueFromY
from
  Table_X x

这仅适用于标量查询 ，这意味着子查询应具有恰好1列，最多1行。 如果行数为0，则ValueFromY将返回NULL ；如果行数超过1，则查询将失败。

select的另一个功能（在SQL Server，MySQL和其他可能的版本中）是，您可以只选择值，而无需完全指定表，如下所示：

Select
  3.14 as MoreOrLessPI

您可以通过编写如下查询来将这两个事实结合起来，将两个计数结合为一个结果：

Select
  (Select query that returns at most 1 row) as Result1,
  (Select another query that returns at most 1 row) as Result2

Answer 2

这应该给您期望的结果：

SELECT * FROM(
(Select Count(*) as StockCountA from Table_A where dept='AAA') StockCountA ,
(Select Count(*) as StockCountB from Table_B where dept='BBB') StockCountB
);

Answer 3

试试下面的SQL：

select (Select Count(*) as StockCountA from Table_A where dept='AAA')  StockCountA, 
       (Select Count(*) as StockCountB from Table_B where dept='BBB')  StockCountB

希望这可以帮助 ：）

Answer 4

虽然并非总是最佳做法，但可以进行交叉加入。

SELECT
COUNT(Table_A.SOME_COLUMN) as StockCountA
,COUNT(Table_B.SOME_COLUMN) as StockCountB
FROM Table_A, Table_B WHERE Table_A.dept='AAA' AND Table_B.dept='BBB'