Question

我的代码是在一定的日期范围内知道我的库存状态，但是我遇到问题，当涉及到库存时它没有返回值。

我在套头衫中没有任何值仍然应该计算股票=已交付 - （已售出+已推出）这是代码。

Select A.prod_name As Product, A.prod_totalPrice As Price, A.prod_category As Category, A.prod_ExpDate As Expiration,
ifnull((Select SUM(itp_needQty) from tbl_itmonpur Where itp_prodID = (Select prod_id from tbl_prod where prod_name = A.prod_name)and itp_statusDelv = 'DELIVERED' and itp_date Between "10/06/2014" and "10/06/2014"),0) As Delivered, 
ifnull((Select SUM(sales_qty) from tbl_sales Where sales_prodID = (Select prod_id from tbl_prod where prod_name = A.prod_name)AND sales_date between"10/06/2014" and "10/06/2014" ),0) As Sold, 
ifnull((Select SUM(po_qty) from tbl_PullOver Where po_prodID = (Select prod_id from tbl_prod where prod_name = A.prod_name) AND po_date between "10/06/2014" and "10/06/2014" ),0) As PullOut, 
ifnull((Select SUM(itp_needQty) from tbl_itmonpur Where itp_prodID = (Select prod_id from tbl_prod where prod_name = A.prod_name)and itp_statusDelv = 'DELIVERED' and itp_date Between "10/06/2014" and "10/06/2014") - ((Select SUM(sales_qty) from tbl_sales Where sales_prodID = (Select prod_id from tbl_prod where prod_name = A.prod_name)AND sales_date between "10/06/2014" and "10/06/2014" ) + (Select SUM(po_qty) from tbl_PullOver Where po_prodID = (Select prod_id from tbl_prod where prod_name = A.prod_name) AND po_date between "10/06/2014" and "10/06/2014")), 0) As Stock,
S.supp_name As Supplier 
From tbl_prod As A 
Inner Join tbl_supp As S 
On A.prod_suppID = S.supp_id 
Group By Product;

我只是一名学生，请对我很轻松。谢谢！

Answer 1

在MySQL中，您可以使用coalesce()函数来处理这种情况：

的 coalesce(value, ...)
  返回列表中的第一个非NULL值，如果没有非NULL值，则返回NULL。

示例：的

select coalesce(1, 2, 3); -- Will return 1 select coalesce(null, 2, 3); -- Will return 2 select coalesce(1, null, 3); -- Will return 1 select coalesce(null, null, null); -- Will return null

计算值不能被看到可能是因为null

1 个答案: