如何在Microsoft SQL Server中划分两个表达式

Question

如何在Microsoft SQL Server中划分两个表达数字作为结果的表达式？我尝试用/，但这没有用

SELECT COUNT(*) FROM A 
SELECT COUNT(*) FROM B WHERE c = 1

我试过/但这没有用

SELECT COUNT(*) 
FROM A/SELECT COUNT(*) FROM B WHERE c = 1

Answer 1

它可能依赖于RDBMS，这适用于sql server。

SELECT ACounts/ CAST(BCounts AS Decimal(29,20))
FROM (SELECT COUNT(*) AS ACounts FROM A) AS suba
, (SELECT COUNT(*) AS BCounts FROM B WHERE c = 1) AS subb

请注意，我将BCounts转换为任意大小的小数，否则它将舍入到最接近的整数。如果那是您想要的，请忽略该部分。

这也有效

SELECT (SELECT COUNT(*) AS ACounts FROM A)/ CAST((SELECT COUNT(*) AS BCounts FROM B WHERE c = 1) AS Decimal(29,20))

Answer 2

使用子查询：

SELECT (a.countA / b.countB) As divisionResult 
FROM 
    (SELECT COUNT(*) AS countA FROM A) a,
    (SELECT COUNT(*) AS countB FROM B WHERE c = 1) b
;