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sql查询帮助-计数

sql-server-2008 sql-server

Gold · 技术社区 · 15 年前

table A , table B , Table C

我需要计算所有3个表,并在一个查询行中看到它,如下所示:

A  B   C
30 40 12

select count(*) from A,select count(*) from B,select count(*) from C

但我错了

4 回复 | 直到 15 年前

Joe Stefanelli 15 年前

select
    (select count(*) from A) as A,
    (select count(*) from B) as B,
    (select count(*) from C) as C

Moo-Juice 15 年前

SELECT *
FROM 
(SELECT COUNT(*) AS A_Count
 FROM A) tmp,
(SELECT COUNT(*) AS B_Count
 FROM B) tmp2, 
(SELECT COUNT(*) AS C_Count
 FROM C) tmp3

Jim Ross 15 年前

SELECT
    A = (SELECT COUNT(*) FROM A),
    B = (SELECT COUNT(*) FROM B),
    C = (SELECT COUNT(*) FROM C)

Dan J 15 年前

其他的解决方案比较干净,但是。。。还有一个办法。:)

SELECT SUM(CASE WHEN TableName = 'A' THEN RecordCount ELSE 0 END) AS A_Count,
SUM(CASE WHEN TableName = 'B' THEN RecordCount ELSE 0 END) AS B_Count,
SUM(CASE WHEN TableName = 'C' THEN RecordCount ELSE 0 END) AS C_Count
FROM
(
    SELECT 'A' AS TableName, COUNT(*) AS RecordCount FROM A
    UNION ALL
    SELECT 'B', COUNT(*) FROM B
    UNION ALL
    SELECT 'C', COUNT(*) FROM C
) q

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