SELECT 平均借阅次数=
(SELECT COUNT(*)
FROM Borrowing)/(SELECT SUM(Bcount) FROM Books)其实做的除法是19/97,可是结果是0.
如果才能得到19/97的小数呢?
解决方案 »
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(SELECT COUNT(*)
FROM Borrowing)*1.0/(SELECT SUM(Bcount) FROM Books)
(SELECT COUNT(*)
FROM Borrowing)*1.0/(SELECT SUM(Bcount) FROM Books)
(SELECT COUNT(*)
FROM Borrowing)*1./(SELECT SUM(Bcount) FROM Books)
1 最简单的方法:
SELECT 平均借阅次数=
(SELECT COUNT(*)
FROM Borrowing)*1.0/(SELECT SUM(Bcount) FROM Books)
2 常规方法:
SELECT 平均借阅次数=
(SELECT cast(COUNT(*) as decimal(18,2))
FROM Borrowing)/(SELECT cast(SUM(Bcount) as decimal(18,2)) FROM Books)
除法值是按它们的精度算的,都为整数,所以结果是0,
可以转换成小数形式!
SELECT 平均借阅次数=
CONVERT(NUMERIC(18,2)) ,(SELECT COUNT(*) FROM Borrowing)/(SELECT SUM(Bcount) FROM Books))