mysql - Computed Value cant be seen maybe because of null -

mysql - Computed Value cant be seen maybe because of null -

my code here know status of inventory on range of date , i'm having problem when comes stock returns no value.

i have no values in pullover still should compute stock = delivered - (sold + pullover) here code.

select a.prod_name product, a.prod_totalprice price, a.prod_category category, a.prod_expdate expiration, ifnull((select sum(itp_needqty) tbl_itmonpur itp_prodid = (select prod_id tbl_prod prod_name = a.prod_name)and itp_statusdelv = 'delivered' , itp_date between "10/06/2014" , "10/06/2014"),0) delivered, ifnull((select sum(sales_qty) tbl_sales sales_prodid = (select prod_id tbl_prod prod_name = a.prod_name)and sales_date between"10/06/2014" , "10/06/2014" ),0) sold, ifnull((select sum(po_qty) tbl_pullover po_prodid = (select prod_id tbl_prod prod_name = a.prod_name) , po_date between "10/06/2014" , "10/06/2014" ),0) pullout, ifnull((select sum(itp_needqty) tbl_itmonpur itp_prodid = (select prod_id tbl_prod prod_name = a.prod_name)and itp_statusdelv = 'delivered' , itp_date between "10/06/2014" , "10/06/2014") - ((select sum(sales_qty) tbl_sales sales_prodid = (select prod_id tbl_prod prod_name = a.prod_name)and sales_date between "10/06/2014" , "10/06/2014" ) + (select sum(po_qty) tbl_pullover po_prodid = (select prod_id tbl_prod prod_name = a.prod_name) , po_date between "10/06/2014" , "10/06/2014")), 0) stock, s.supp_name supplier tbl_prod inner bring together tbl_supp s on a.prod_suppid = s.supp_id grouping product;

i'm pupil please easy on me. give thanks you!

in mysql can utilize coalesce() function deal kind of situations:

coalesce(value, ...)

returns first non-null value in list, or null if there no non-null values.

example:

class="lang-sql prettyprint-override">select coalesce(1, 2, 3); -- homecoming 1 select coalesce(null, 2, 3); -- homecoming 2 select coalesce(1, null, 3); -- homecoming 1 select coalesce(null, null, null); -- homecoming null

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