SQL字段拼接与拆分

--测试数据：
create table #tojoin(
    tablename varchar(20) not null,
    columnname varchar(20) not null,
    primary key clustered(tablename,columnname))
go
create table #tosplit(
    tablename varchar(20) not null primary key clustered,
    columnnames varchar(max) not null)
go
insert into #tojoin values(‘tblemployee‘,‘employeecode‘)
insert into #tojoin values(‘tblemployee‘,‘employeename‘)
insert into #tojoin values(‘tblemployee‘,‘hiredate‘)
insert into #tojoin values(‘tblemployee‘,‘jobcode‘)
insert into #tojoin values(‘tblemployee‘,‘reporttocode‘)
insert into #tojoin values(‘tbljob‘,‘jobcode‘)
insert into #tojoin values(‘tbljob‘,‘jobtitle‘)
insert into #tojoin values(‘tbljob‘,‘joblevel‘)
insert into #tojoin values(‘tbljob‘,‘departmentcode‘)
insert into #tojoin values(‘tbldepartment‘,‘departmentcode‘)
insert into #tojoin values(‘tbldepartment‘,‘departmentname‘)
go
insert into #tosplit values(‘tbldepartment‘,‘departmentcode,departmentname‘)
insert into #tosplit values(‘tblemployee‘,‘employeecode,employeename,hiredate,jobcode,reporttocode‘)
insert into #tosplit values(‘tbljob‘,‘departmentcode,jobcode,joblevel,jobtitle‘)
go
--拼接(join)，sql server 2005的for xml扩展可以将一个列表转成一个字串：
select
    t.tablename,
    columnnames = stuff(
        (select ‘,‘ + c.columnname
        from #tojoin c
        where c.tablename = t.tablename
        for xml path(‘‘)),
        1,1,‘‘)
from #tojoin t
group by t.tablename
--切分(split)，使用sql server 2005对xquery的支持：
select
    t.tablename,
    columnname = c.columnname.value(‘.‘,‘varchar(20)‘)
from (
    select
        tablename,
        columnnamesxml = cast(‘<root>‘ + replace((select columnname = columnnames for xml path(‘‘)),‘,‘,‘</columnname><columnname>‘) + ‘</root>‘ as xml)
    from #tosplit
) t
cross apply t.columnnamesxml.nodes(‘/root/columnname‘) c(columnname)