begin
    if @Type='All'
        select  a.*,  b. MenuName as PMenuName from SysMenu a left join SysMenu b  on a.PMenuID=b.MenuID where a.Status='Y' order by cast(a.MenuID as int)
    else if @Type='Single'
        select  a.*,  b. MenuName as PMenuName from SysMenu a left join SysMenu b  on a.PMenuID=b.MenuID where a.MenuID=@FieldValue
    else
        select  a.*,  b. MenuName as PMenuName from SysMenu a left join SysMenu b  on a.PMenuID=b.MenuID where a.Status='Y' order by cast(a.MenuID as int)
end


加粗部份為何需要這樣來鏈接自已呢？？在什麼情況下需要這樣鏈接查詢呢？

還是有點沒有看明白是什麼意思!呵呵!

明白了。謝謝指導

drop table shiyan
go
create table shiyan(id int)
insert into shiyan select 333
insert into shiyan select 333
insert into shiyan select 333
insert into shiyan select 333
insert into shiyan select 333
insert into shiyan select 333
select * from shiyan
declare @id int
update shiyan set @id=isnull(@id,id),id=@id-100,@id=@id+100
 
subMain上面語句中。後面的update語句是如何理解呢？》我知道是更新表中的數據，，但是。set後面的語句就不明白是什麼意思啦！