使用变量进行字符串汇总 [英] String aggregate using a variable

问题描述

可以使用一个变量来连接多个行中的值（作为隐式聚合函数）吗？

Is is okay to use a variable to concatenate a value from several rows ( as an implicit aggregate function )? It seems to work fine on my machine, but I haven't seen it recommended.

declare @v_str varchar(4000) = ''
select top 5 @v_str = @v_str + ',' + city_name from city_table order by city_name
print @v_str

推荐答案

来自 nvarchar串联/索引/ nvarchar（最大值）莫名其妙的行为
未定义聚合级联查询的正确行为。

From nvarchar concatenation / index / nvarchar(max) inexplicable behavior "The correct behavior for an aggregate concatenation query is undefined."

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