Question

非常新的SQL，但我需要一些帮助，我确信这是一个简单的修复。

我在表格中有一列数据名为＆＃39; Produce＆＃39;将水果类型存储在名为“Fruit＆＃39;”的列中。此列中的某些值以逗号分隔。

有没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？

E.g。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，但我认为我已完全使用它。任何人都可以帮忙提供一些解释，如何做到这一点，拜托？如果有帮助，我正在使用T-SQL。

提前致谢。

Answer 1

要解决的核心问题是停止将您的值存储为逗号分隔列表。保持数据规范化。说到这一点......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,',')

功能

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

Jeff Moden Article for Function

Answer 2

这可以使用纯SQL完成，无需用户编写的函数。

SQL Server

WITH
    fruittable
    AS
        (   SELECT 'Apple' fruit, 1 id
         UNION ALL
            SELECT 'Banana,Apple', 2
         UNION ALL
            SELECT 'Tomato,Grapefruit,Apple', 3
         UNION ALL
            SELECT 'Watermelon,Persimmons', 4
          ),
    split (fruit, id, leftover)
    AS
        (SELECT case when len(fruit) = 0 or fruit is null then null else left(fruit + ',',  charindex(',',fruit + ',') -1 ) end AS fruit
              , id
              , case when len(fruit) = 0 or fruit is null then null else right(fruit + ',', len(fruit) - charindex(',',fruit + ',') + 1) end as leftover
           FROM fruittable
         UNION ALL
         SELECT case when len(leftover) = 0 or leftover is null then null else left(leftover,  charindex(',',leftover) - 1) end AS fruit
              , id
              , case when len(leftover) = 0 or leftover is null then null else substring(leftover,  charindex(',',leftover) + 1, len(leftover)) end as leftover
           FROM split
          WHERE fruit IS NOT NULL)
SELECT fruit, id
  FROM split where fruit is not null
  order by fruit, id;

<强>的Oracle

WITH
    fruittable
    AS
        (SELECT 'Apple' fruit, 1 id
           FROM DUAL
         UNION ALL
         SELECT 'Banana,Apple', 2
           FROM DUAL
         UNION ALL
         SELECT 'Tomato,Grapefruit,Apple', 3
           FROM DUAL
         UNION ALL
         SELECT 'Watermelon,Persimmons', 4
           FROM DUAL),
    split (fruit, id, leftover)
    AS
        (SELECT SUBSTR (fruit || ',', 1, INSTR (fruit || ',', ',') - 1) AS fruit
              , id
              , SUBSTR (fruit || ',', INSTR (fruit || ',', ',') + 1) AS leftover
           FROM fruittable
         UNION ALL
         SELECT SUBSTR (leftover, 1, INSTR (leftover, ',') - 1) AS fruit
              , id
              , SUBSTR (leftover, INSTR (leftover, ',') + 1) AS leftover
           FROM split
          WHERE fruit IS NOT NULL)
  SELECT fruit, id
    FROM split
   WHERE fruit IS NOT NULL
ORDER BY fruit, id

SQL Sting拆分为单列

2 个答案: