两个常用的SQL语句(查询最大值、取得子结点)

查询一组数据中的最大值

declare @T table(so_no nvarchar(10), so_date datetime, curr_code nvarchar(5), cust_code nvarchar(10), item_no nvarchar(20), qty numeric(9), unit_price numeric(9), uom nvarchar(4), ftd datetime)

insert into @T select a.so_no , a.curr_code,a.so_date, a.cust_code ,b.item_no,b.qty,b.unit_price,b.uom,b.ftd from SOHEAD a, SODETAIL b where a.so_no = b.so_no

select * from @T c where
not exists(select 1 from @T d where c.so_no = d.so_no and Datediff(dd,c.ftd,d.ftd)>0)

取得某一结点下的所有子结点的记录。

--根据图书名称和种类得到图书信息
CREATE PROCEDURE GetBookByNameAndCategory
(
@FullName NVARCHAR(200),
@Category INT
)
AS
BEGIN
IF @Category <> -1
BEGIN
create table #T(
[ID] int,
ParentID int,
[Level] INT
)

declare @strCategory nvarchar(10)
set @strCategory='' + @category

declare @s nvarchar(4000)

set @s = N'declare @i int set @i = 1
insert into #T select pkid,parentid,@i from tBookCategory where PKID='+ @strCategory +N'
while @@rowcount<>0
begin
set @i = @i + 1

insert into #t
select
a.pkid,a.parentid,@i
from tBookCategory a,#t b
where a.parentid=b.id and b.Level = @i-1
end'
exec(@s)

select tBook.*
from #T a,tBook
where a.[id]=tBook.Category
AND (@FullName is null or @FullName='' or tBook.FullName like '%'+@FullName+'%')
END
ELSE
BEGIN
SELECT * FROM tBook where @FullName is null or @FullName='' or tBook.FullName like '%'+@FullName+'%'
END
END