Question

我有一个查询从表中返回合理数量的记录。我需要包含逗号分隔的字符串作为输出列。像这样的东西

SELECT
 column1,
 column2,
 column3,
 [Delimited string based on the id]
FROM
  sometable
WHERE
  id = someid

我知道你可以使用我过去使用过的coalesce函数但是我不确定如何将它集成到select语句中，还不能确定性能吗？

有什么想法吗？

Answer 1

我遍历项目以构建字符串，然后将其添加到结果集中。

-- Minor performance tweak.
SET NOCOUNT ON
GO

-- ID of the item or widget or whatever 
DECLARE @someid int    

DECLARE @LookupItems TABLE
(
    ID int IDENTITY (1, 1) PRIMARY KEY NOT NULL,
    LookupTableID int,          -- Primary key of the lookup table.
    LookupField varchar(30)     -- Text of the lookup value.
)

-- Update to the desired id.
SET @someid = 1234

INSERT INTO @LookupItems (ID, LookupField)
SELECT ID, Value
FROM dbo.somelookuptable
WHERE ID IN (

    SELECT lookupid
    FROM dbo.sometable
    WHERE ID = @someid

)

DECLARE 
    @Count int, 
    @Max int, 
    @DelimitedString varchar(1000)

-- Initialize with a non-NULL value to facilitate concatenation.
SET @DelimitedString = ''  

SET @Count = 1
SELECT @Max = MAX(ID) FROM @LookupItems

WHILE (@Count <= @Max)
BEGIN

    SELECT @DelimitedString = @DelimitedString + IsNull(somefield, '') + ','
    FROM @LookupItems
    WHERE ID = @Count

    SET @Count = @Count + 1

END

SELECT
    column1,
    column2,
    column3,
    @DelimitedString 
FROM dbo.sometable
WHERE id = someid

如何在SQL Server 2000中构建逗号分隔的字符串？

1 个答案: