Question

如何在SQL Server中使用DISTINCT关键字？我的意思是它是否适用于特定领域。

select id, name, age 
from dbo.XXX

查询返回了多行。我想知道有多少种身份证或姓名或年龄。

select **distinct** id, name, age from dbo.XXX或 select id, **distinct** name, age from dbo.XXX或 select id, name, **distinct** age from dbo.XXX

总而言之，我想使用单个SQL来获取每个字段的不同计数，例如select id, name, age from dbo.XXX

Answer 1

Dense_Rank可用于计算任何列和多列的不同计数：

Select col1, col2, col3,
    dense_rank() over (partition by [col1] order by [Unique ID]) + dense_rank() over (partition by [col1] order by [Unique ID] desc) - 1 as DistCountCol1,
    dense_rank() over (partition by [col2] order by [Unique ID]) + dense_rank() over (partition by [col2] order by [Unique ID] desc) - 1 as DistCountCol2,
    dense_rank() over (partition by [col3] order by [Unique ID]) + dense_rank() over (partition by [col3] order by [Unique ID] desc) - 1 as DistCountCol3
from [table]

Answer 2

select distinct ID
from dbo.XXX

Select distinct name
from dbo.XXX

Select distinct age
from dbo.XXX

如果您想知道每个不同的ID或名称或年龄有多少行，您可以使用以下内容：

Select ID, count(id) as [ID_Recurrence]
from dbo.XXX
group by ID

Select Age, count(age) as [Age_Recurrence]
from dbo.XXX
group by Age

Select Name, count(name) as [Name_Recurrence]
from dbo.XXX
group by Name

Answer 3

DISTINCT关键字返回一个唯一的行，如下面的

SELECT DISTINCT ID FROM SomeTable
SELECT DISTINCT ID , SCORE FROM SomeTable

如果您想从行获取唯一值，请尝试以下代码。

以下代码是从here

复制而来的

select t.id, t.player_name, t.team
from tablename t
join (select team, min(id) as minid from tablename group by team) x
on x.team = t.team and x.minid = t.id

Answer 4

select COUNT(distinct id) uniqueIDCount
from dbo.XXX

将计算id字段的不同值，如果要计算字段组合的不同值，则必须连接字段，假设id为整数且name为nvarchar：

select COUNT(distinct CONVERT(nvarchar, id) + name) uniqueIDCount
from dbo.XXX

请注意，即使这种方式看起来不错，它可能不是最有效的方法，在这里你有更高效，但也更复杂的方法：

with c as (
    select distinct id, name
    from dbo.XXX
)select COUNT(1)
from c

Answer 5

不确定为什么它很复杂。你可以有3个不同的查询，如果你愿意，你可以联合返回单集。

如何在SQL Server中使用DISTINCT关键字？

5 个答案: