--存储过程创建语法...

begin tran
select a.listid,b.productid
from IM_Out a join IM_OutDetail b on a.id = b.out_id
where a.id = ?
  and not exists (select 1 from IM_Stock where warehouseid = a.warehouseid 
                              and product_id = b.product_id and quantity >= b.quantity)

if @@rowcount > 0
    begin
        commit tran
        return
    end
else
        begin
                --update  更新库存量
                update c
                set c.quantity = c.quantity - b.quantity
                from IM_Out a join IM_OutDetail b on a.id = b.out_id
                              join IM_Stock c on a.warehouseid = c.warehouseid and b.product_id = c.product_id
                where a.id = ?
                commit tran
        end

------解决方案--------------------

if (查找库存的数量)> 0
begin
	if 查找库存的数量 >要出货的数量
	begin
		update 库存表
		set    库存数量 = 库存数量 - 要出货的数量
		where  出货单 = 传入参数
		
		insert into 库存记录表  
		select 出货单,要出货的数量,进出类型标记  
	end
	else
	begin
		RAISERROR('库存有，但是不足出货', 18, 1)
	end
end
else
begin
	RAISERROR('库存为0', 18, 1)
end