对sql很新,但我需要一些帮助,我确信这是一个简单的修复.
我在一个名为’Produce’的表中有一列数据,其中的水果类型存储在名为’Fruit’的列中.此列中的某些值以逗号分隔.
是否有一种简单的方法来拆分下面的结果,以便结果作为一列唯一条目？
例如.示例表
Fruit ----- Apple Plum Pear,Mango Pear
我希望返回的内容如下：
Fruit ----- Apple Plum Pear Mango
我曾尝试使用字符串拆分功能,但我想我已完全使用它.任何人都可以帮忙提供一些解释,如何做到这一点,好吗？如果有帮助,我正在使用T-sql.
提前致谢.
解决方法
要修复的核心问题是停止将值存储为逗号分隔列表.保持数据规范化.有了这样说……每个人都需要一个好的分裂器……
declare @table table (Fruit varchar(64))
insert into @table
values
('Apple'),('Plum'),('Pear,Mango'),('Pear')
select distinct
Item
from
@table
cross apply
dbo.DelimitedSplit8K(Fruit,',')
或者,如果您使用的是sql Server 2016 …
select distinct
Item
from
@table
cross apply
string_split(Fruit,')
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE FUNCTION [dbo].[DelimitedSplit8K] (@pString VARCHAR(8000),@pDelimiter CHAR(1))
--WARNING!!! DO NOT USE MAX DATA-TYPES HERE! IT WILL KILL PERFORMANCE!
RETURNS TABLE WITH SCHEMABINDING AS
RETURN
/* "Inline" CTE Driven "Tally Table" produces values from 1 up to 10,000...
enough to cover VARCHAR(8000)*/
WITH E1(N) AS (
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
),--10E+1 or 10 rows
E2(N) AS (SELECT 1 FROM E1 a,E1 b),--10E+2 or 100 rows
E4(N) AS (SELECT 1 FROM E2 a,E2 b),--10E+4 or 10,000 rows max
cteTally(N) AS (--==== This provides the "base" CTE and limits the number of rows right up front
-- for both a performance gain and prevention of accidental "overruns"
SELECT TOP (ISNULL(DATALENGTH(@pString),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4
),cteStart(N1) AS (--==== This returns N+1 (starting position of each "element" just once for each delimiter)
SELECT 1 UNION ALL
SELECT t.N+1 FROM cteTally t WHERE SUBSTRING(@pString,t.N,1) = @pDelimiter
),cteLen(N1,L1) AS(--==== Return start and length (for use in substring)
SELECT s.N1,ISNULL(NULLIF(CHARINDEX(@pDelimiter,@pString,s.N1),0)-s.N1,8000)
FROM cteStart s
)
--===== Do the actual split. The ISNULL/NULLIF combo handles the length for the final element when no delimiter is found.
SELECT ItemNumber = ROW_NUMBER() OVER(ORDER BY l.N1),Item = SUBSTRING(@pString,l.N1,l.L1)
FROM cteLen l
;
GO
