MySQL 字符串拆分操作(含分隔符的字符串截取)

SELECT LEFT(SUBSTRING('P1111',help_topic_id+1),1) AS num FROM mysql.help_topic WHERE help_topic_id < LENGTH('P1111');

SUBSTRING_INDEX('7654,7698,7782,7788',',',2)

SUBSTRING_INDEX('7654,7698,7782,7788',',',-2)

REPLACE('7654,7698,7782,7788',',','')

LENGTH('7654,7698,7782,7788')

SELECT 
 SUBSTRING_INDEX(SUBSTRING_INDEX('7654,7698,7782,7788',',',help_topic_id+1),',',-1) AS num 
FROM 
 mysql.help_topic 
WHERE 
 help_topic_id < LENGTH('7654,7698,7782,7788')-LENGTH(REPLACE('7654,7698,7782,7788',',',''))+1

help_topic_id < LENGTH('7654,7698,7782,7788')-LENGTH(REPLACE('7654,7698,7782,7788',',',''))+1

SUBSTRING_INDEX(SUBSTRING_INDEX('7654,7698,7782,7788',',',help_topic_id+1),',',-1) AS num 

SUBSTRING_INDEX('7654,7698,7782,7788',',',help_topic_id+1)

SUBSTRING_INDEX(SUBSTRING_INDEX('7654,7698,7782,7788',',',help_topic_id+1),',',-1)

create function f_split(@c varchar(2000),@split varchar(2))
returns @t table(col varchar(20))
as
begin
while(charindex(@split,@c)<>0)
begin
insert @t(col) values (substring(@c,1,charindex(@split,@c)-1))
set @c = stuff(@c,@c),'')
end
insert @t(col) values (@c)
return
end
go
select * from dbo.f_split('dfkd,dfdkdf,dfdkf,dffjk',',')
drop function f_split
col
--------------------
dfkd
dfdkdf
dfdkf
dffjk

CREATE function Get_StrArrayLength
(
@str varchar(1024),--要分割的字符串
@split varchar(10) --分隔符号
)
returns int
as
begin
declare @location int
declare @start int
declare @length int
set @str=ltrim(rtrim(@str))
set @location=charindex(@split,@str)
set @length=1
while @location<>0
begin
set @start=@location+1
set @location=charindex(@split,@str,@start)
set @length=@length+1
end
return @length
end

select dbo.Get_StrArrayLength('78,2,3',')

CREATE function Get_StrArrayStrOfIndex
(
@str varchar(1024),--要分割的字符串
@split varchar(10),--分隔符号
@index int --取第几个元素
)
returns varchar(1024)
as
begin
declare @location int
declare @start int
declare @next int
declare @seed int
set @str=ltrim(rtrim(@str))
set @start=1
set @next=1
set @seed=len(@split)
set @location=charindex(@split,@str)
while @location<>0 and @index>@next
begin
set @start=@location+@seed
set @location=charindex(@split,@start)
set @next=@next+1
end
if @location =0 select @location =len(@str)+1
--这儿存在两种情况：1、字符串不存在分隔符号 2、字符串中存在分隔符号，跳出while循环后，@location为0，那默认为字符串后边有一个分隔符号。
return substring(@str,@start,@location-@start)
end

select dbo.Get_StrArrayStrOfIndex('8,9,4',2)

declare @str varchar(50)
set @str='1,3,4,5'
declare @next int
set @next=1
while @next<=dbo.Get_StrArrayLength(@str,')
begin
print dbo.Get_StrArrayStrOfIndex(@str,@next)
set @next=@next+1
end