Question

我有2个表，T1和T2。我想加入这两个表，只返回2行数据，将Item中的整数替换为T2的查找值。

表T1

Item    Date
------  ---------
1;4;5;  3/13/2013
1;2;3;  3/13/2013

表T2

ID    Desc
----  ------
1     Tree
2     Grass
3     Sand
4     Water
5     Bridge

预期结果：

Item                 Date 
------------------   ---------
Tree;Water;Bridge;   3/13/2013
Tree;Grass;Sand;     3/13/2013

Answer 1

首先，创建一个Split函数，它返回一个整数和一个保持顺序的序列号。这是一个例子：

ALTER FUNCTION dbo.SplitInts
(
    @List       VARCHAR(MAX),
    @Delimiter  VARCHAR(32)
)
RETURNS TABLE
AS
    RETURN 
    (
      SELECT rn = ROW_NUMBER() OVER (ORDER BY Number), 
      Item = CONVERT(INT, Item)
        FROM (SELECT Number, Item = LTRIM(RTRIM(SUBSTRING(@List, Number, 
          CHARINDEX(@Delimiter, @List + @Delimiter, Number) - Number)))
        FROM (SELECT ROW_NUMBER() OVER (ORDER BY [object_id])
          FROM sys.all_objects) AS n(Number)
        WHERE Number <= CONVERT(INT, LEN(@List))
        AND SUBSTRING(@Delimiter + @List, Number, 1) = @Delimiter
      ) AS y
    );
GO

然后以下查询执行您所追求的内容：

DECLARE @t1 TABLE
(
 Item VARCHAR(MAX),
 [Date] DATE -- terrible column name!
);

INSERT @t1 VALUES('1;4;5;','20130313'),('1;2;3;','20130313');
-- please use unambiguous date formats!

DECLARE @t2 TABLE
(
 ID INT, -- another bad column name - what kind of ID?
 [Desc] VARCHAR(255)  -- another bad column name, this is a keyword!
);

INSERT @t2 VALUES(1,'Tree'),(2,'Grass'),
(3,'Sand'),(4,'Water'),(5,'Bridge');

;WITH x AS
(
  SELECT t1.Item, Date, t2ID = i.Item, i.rn, n = t2.[Desc] 
  FROM @t1 AS t1 CROSS APPLY dbo.SplitInts(t1.Item, ';') AS i
  INNER JOIN @t2 AS t2 ON i.Item = t2.ID
)
SELECT DISTINCT Item = (
  SELECT n + ';' FROM x AS x2 
  WHERE x.Item = x2.Item
  ORDER BY x2.rn FOR XML PATH, TYPE
).value('.[1]', 'varchar(max)'), [Date]
FROM x;

强烈建议您查看规范化。以分号分隔的列表是将独立值集合在一起的可怕方式。

使用查找表中的值重新组合连接列表

1 个答案: