在数据库中将字表中的多行合并到一列中

create table Post
(
    [PostID] int identity(1,1) primary key not null,
    [Title] nvarchar(50),
    [Content] text,
    [CreateDate] datetime default getdate()
)

create table Comments
(
    [CommentID] int identity(1,1) primary key not null,
    [PostID] int,
    [Content] text,
    [CreateDate] datetime default getdate()
)

insert into Post select '钓鱼岛是中国的吗？','钓鱼岛是中国的',getdate()
insert into Comments select 1,'绝对是',getdate()
insert into Comments select 1,'必须是的',getdate()
insert into Comments select 1,'谁说不是呢',getdate()

create  FUNCTION fn_GetAllComments(@PostID int)
RETURNS NVARCHAR(4000)
AS
BEGIN
    DECLARE @result VARCHAR(4000)
    SET @result=''
    DECLARE getAllComments CURSOR
    FOR
        select CommentID from Comments where PostID=@PostID
    OPEN getAllComments
    DECLARE @ID SYSNAME
    FETCH  FROM getAllComments INTO @ID
    WHILE @@fetch_status=0
    BEGIN
        SET @result=@result+(select convert(nvarchar(20),CreateDate,120)
                                from Comments where CommentID=@ID)+':'+
                            (select cast([Content] as nvarchar(4000))
                                from Comments where CommentID=@ID)+'；'
        FETCH  FROM getAllComments INTO @ID
    END
    CLOSE getAllComments
    SET @result= substring(@result,0,len(@result))
    DEALLOCATE getAllComments
    RETURN @result
END

select
    Title,[Content],CreateDate,dbo.fn_GetAllComments(PostID) as AllComments
from Post