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問題描述
我有這個(gè)查詢:
SELECT
Count(*) as Cnt,
Category
FROM [MyDb].[dbo].[MyTable]
group by Category
order by Cnt
它為我提供了每個(gè) Category 中的行數(shù).現(xiàn)在我想添加第三列，它會(huì)給我 Cnt/(此表中的總行數(shù)).
It gives me count of rows in each Category. Now I would like to add a third column that would give me Cnt / (total rows in this table).
我該怎么做?
推薦答案
你可以用子查詢來做到:
you could do it with a subquery:
SELECT Count(*) as Cnt, Category,
(Cast(Count(*) as real) / cast((SELECT Count(*) FROM [MyDb].[dbo].[MyTable]) as real)) AS [Percentage]
FROM [MyDb].[dbo].[MyTable]
group by Category
order by Cnt
或使用變量:
declare @total real;
select @total = count(*) from [MyDb].[dbo].[MyTable];
SELECT Count(*) as Cnt, Category, (Cast(Count(*) as real) / @total) AS [Percentage]
FROM [MyDb].[dbo].[MyTable]
group by Category
order by Cnt
我在兩個(gè)示例中都將 count(*) 轉(zhuǎn)換為實(shí)數(shù)以避免整數(shù)除法類型問題.
I've cast count(*) as real in both examples to avoid integer-division type issues.
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