for xml path

示例表 tb 数据如下

id value

—————

1 aa

1 bb

2 aaa

2 bbb

2 ccc

第一种

SELECT id,

[val]=( SELECT [value] +','

FROM tb AS b

WHERE b.id = a.id

FOR XML PATH('') )

FROM tb AS a

第一种显示结果

1 aa,bb,

1 aa,bb,

2 aaa,bbb,ccc,

2 aaa,bbb,ccc,

2 aaa,bbb,ccc,第二种

SELECT id,

[val]=( SELECT [value] +','

FROM tb AS b

WHERE b.id = a.id

FOR XML PATH('') )

FROM tb AS a

GROUP BY id

第二种显示结果

1 aa,bb,

2 aaa,bbb,ccc,第三种 （用STUFF函数替换掉首端的逗号）

SELECT id,

[val]=STUFF( (SELECT ','+[value]

FROM tb AS b

WHERE b.id = a.id

FOR XML PATH('')) , 1 , 1 , '' )

FROM tb AS a

GROUP BY id

第三种显示结果

1 aa,bb

2 aaa,bbb,cccSTUFF 函数将字符串插入另一字符串。它在第一个字符串中从开始位置删除指定长度的字符；然后将第二个字符串插入第一个字符串的开始位置。

STUFF ( character_expression , start , length ,character_expression_insert )

第四种 （用REPLACE函数将所有空格替换成逗号）

SELECT id,

[val]= REPLACE( (SELECT [value] AS [data()]

FROM tb AS b

WHERE b.id = a.id

FOR XML PATH('')) , ' ', ',')

FROM tb AS a

GROUP BY id