库存先进先出简单例子

-- 库存先进先出简单例子：

create table t(
id int identity ( 1 , 1 ),
name varchar ( 50 ), -- 商品名称
j int ,        -- 入库数量
c int ,        -- 出库数量
jdate datetime -- 入库时间
)
insert into t(name,j,c,jdate) select   ' A ' , 100 , 0 , ' 2007-12-01 '
insert into t(name,j,c,jdate) select   ' A ' , 200 , 0 , ' 2008-01-07 '
insert into t(name,j,c,jdate) select   ' B ' , 320 , 0 , ' 2007-12-21 '
insert into t(name,j,c,jdate) select   ' A ' , 100 , 0 , ' 2008-01-15 '
insert into t(name,j,c,jdate) select   ' B ' , 90 , 0 , ' 2008-02-03 '
insert into t(name,j,c,jdate) select   ' A ' , 460 , 0 , ' 2008-02-01 '
insert into t(name,j,c,jdate) select   ' A ' , 510 , 0 , ' 2008-03-01 '
go



create proc wsp
@name varchar ( 50 ), -- 商品名称
@cost int          -- 销售量
as
-- 先得出该货物的库存是否够
declare @spare float -- 剩余库存
select @spare = sum (j) - sum (c) from t where name = @name
if ( @spare >= @cost )
begin
    -- 根据入库日期采用先进先出原则对货物的库存进行处理
    update t set c =
    case when ( select @cost - isnull ( sum (j), 0 ) + isnull ( sum (c), 0 ) from t where name = @name and jdate <= a.jdate and j != c) >= 0
    then a.j
    else
        case when ( select @cost - isnull ( sum (j), 0 ) + isnull ( sum (c), 0 ) from t where name = @name and jdate < a.jdate and j != c) < 0 then 0
        else ( select @cost - isnull ( sum (j), 0 ) + isnull ( sum (c), 0 ) + a.c from t where name = @name and jdate < a.jdate and j != c)
        end
    end
    from t a where name = @name and j != c
end
else
    raiserror ( ' 库存不足 ' , 16 , 1 )   
    return
go


-- 测试：

exec wsp @name = ' A ' , @cost = 180
select * from t


-- drop table t
-- drop proc wsp