SQL：組合從多個表中選擇計數（*）

Question

如何將來自不同表的多個選擇計數（*）組合成一個回報？

我和這篇文章有類似的情結

但我想要一次回歸。

我嘗試了所有的聯盟，但它吐了3個不同的計數行。 你如何將它們合二為一？

select count(*) from foo1 where ID = '00123244552000258'
union all 
select count(*) from foo2 where ID = '00123244552000258'
union all
select count(*) from foo3 where ID = '00123244552000258'

編輯：我在MS SQL 2005上

Answer 1

SELECT 
(select count(*) from foo1 where ID = '00123244552000258')
+
(select count(*) from foo2 where ID = '00123244552000258')
+
(select count(*) from foo3 where ID = '00123244552000258')

這是一種簡單的方法。

Answer 2

select 
  (select count(*) from foo) as foo
, (select count(*) from bar) as bar
, ...

Answer 3

我很驚訝沒有人建議這種變化：

SELECT SUM(c)
FROM (
  SELECT COUNT(*) AS c FROM foo1 WHERE ID = '00123244552000258'
  UNION ALL
  SELECT COUNT(*) FROM foo2 WHERE ID = '00123244552000258'
  UNION ALL
  SELECT COUNT(*) FROM foo3 WHERE ID = '00123244552000258'
);

Answer 4

基本上，您將計數作為標准選擇中的子查詢。

一個例子如下，這將返回1行，兩列

SELECT
 (SELECT COUNT(*) FROM MyTable WHERE MyCol = 'MyValue') AS MyTableCount,
 (SELECT COUNT(*) FROM YourTable WHERE MyCol = 'MyValue') AS YourTableCount,

Answer 5

你可以像以前那樣合並你的計數，但是你可以通過多種方式對它們進行總結，其中一種如下所示：

SELECT SUM(A) 
FROM
(
    SELECT 1 AS A
    UNION ALL 
    SELECT 1 AS A
    UNION ALL
    SELECT 1 AS A
    UNION ALL
    SELECT 1 AS A
) AS B

Answer 6

您可以命名所有字段並在這些字段上添加外部選擇：

SELECT A, B, C FROM ( your initial query here ) TableAlias

這應該夠了吧。

Answer 7

select sum(counts) from (
select count(1) as counts from foo 
union all
select count(1) as counts from bar)

Answer 8

對於oracle：

select( 
select count(*) from foo1 where ID = '00123244552000258'
+
select count(*) from foo2 where ID = '00123244552000258'
+
select count(*) from foo3 where ID = '00123244552000258'
) total from dual;