sql - 插入所有输入项组合的最佳方法

Question

我有一个看起来像这样的表:

firstname    lastname      address      city
    a          b           (c,d,e)      (f,g,h)

我想制作一系列这样的插页:

insert (a,b,c,f)
insert (a,b,c,g)
insert (a,b,c,h)
insert (a,b,d,f)
insert (a,b,d,g)
insert (a,b,e,h)
....

在 SQL Server 中不使用多个游标的最佳方法是什么？

Answer 1

只需使用 cross apply用你的表和一些字符串拆分udf。
您可以在 this article. 中找到最适合您的一款

我在本次演示中使用了我链接到的文章中的 SplitStrings_Moden 函数:

CREATE FUNCTION dbo.SplitStrings_Moden
(
   @List NVARCHAR(MAX),
   @Delimiter NVARCHAR(255)
)
RETURNS TABLE
WITH SCHEMABINDING AS
RETURN
  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),
       E2(N)        AS (SELECT 1 FROM E1 a, E1 b),
       E4(N)        AS (SELECT 1 FROM E2 a, E2 b),
       E42(N)       AS (SELECT 1 FROM E4 a, E2 b),
       cteTally(N)  AS (SELECT 0 UNION ALL SELECT TOP (DATALENGTH(ISNULL(@List,1))) 
                         ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E42),
       cteStart(N1) AS (SELECT t.N+1 FROM cteTally t
                         WHERE (SUBSTRING(@List,t.N,1) = @Delimiter OR t.N = 0))
  SELECT Item = SUBSTRING(@List, s.N1, ISNULL(NULLIF(CHARINDEX(@Delimiter,@List,s.N1),0)-s.N1,8000))
    FROM cteStart s;

一旦你有了拆分功能，你所要做的就是从你的表中选择值，并为你拥有的每个逗号分隔的列使用交叉应用这个功能:

-- INSERT INTO MyTable(firstname, lastname, address, city)
SELECT firstname, lastname, a.item, b.item
FROM MyTable
cross apply dbo.SplitStrings_Moden([address], ',') a
cross apply dbo.SplitStrings_Moden(city, ',') b

See fiddle here