提供字符串的替代聚合函數(shù)
–功能:提供字符串的替代聚合函數(shù)
–說明:例如,將下列數(shù)據(jù)
–test_id test_value
——————–
‘a’ ‘01,03,04’
‘a’ ‘02,04’
‘b’ ‘03,04,08’
‘b’ ‘06,08,09’
‘c’ ’09’
‘c’ ’10’
–轉(zhuǎn)換成test_vlaue列聚合后的函數(shù)，且聚合后的字符串中的值不重復(fù)
–test_id test_value
——————–
‘a’ ‘01,03,04,02’
‘b’ ‘03,04,08,06,09’
‘c’ ‘09,10’
–代碼——————————————-GO
GO
if object_id(N’dbo.merge’,N’FN’) is not null
drop function dbo.merge
GO
–函數(shù)功能:字符串聚合及去除重復(fù)值
create function dbo.merge
(
@test_id varchar(50)
)
returns varchar(50)
as
begin
–字符串聚合————————-START
declare @s varchar(8000)
set @s = ”
select
@s = @s + test_value + ‘,’
from test_a
where test_id = @test_id
–字符串聚合————————-END
–去除重復(fù)值————————-START
declare @value varchar(8000)–存儲第一個逗號前的值
declare @result varchar(8000)–存儲唯一值的中間字符串
set @result = ”
–有值的場合
while charindex(‘,’,@s) 0
begin
–取第一個逗號前的值
set @value = left(@s,charindex(‘,’,@s) -1)
–第一個逗號前的值沒在結(jié)果中出現(xiàn)
if charindex(‘,’ + @value + ‘,’,’,’ + @result) = 0
begin
–加入中間字符串
set @result = @result + @value + ‘,’
end
–去除第一個值以及后面的逗號(剔除法),繼續(xù)循環(huán)判斷
set @s = right(@s,(len(@s) – charindex(‘,’,@s)))
end
set @s = @result
–去除重復(fù)值————————-END
return left(@s,len(@s)-1)
end
GO
if object_id(N’test_a’,N’U’) is not null
drop table test_a
GO
create table test_a
(
test_id varchar(50),
test_value varchar(50)
)
insert into test_a
select ‘a’,’01,03,04′ union all
select ‘a’,’02,04′ union all
select ‘b’,’03,04,08′ union all
select ‘b’,’06,08,09′ union all
select ‘c’,’09’ union all
select ‘c’,’10’
select
test_id,
test_value = dbo.merge(test_id)
from test_a
group by test_id
