在銷售和購買之間的每一行中找出餘額數量

Question

我需要幫助來查找MySql查詢中減去銷售數量後產品數量的數量。這裏是我的查詢：

SELECT 
eng_stock.doc_id, 
eng_vouchers_detail.prod_id, 
GREATEST(
eng_stock.purch_date, 
eng_stock.sale_date 
) AS vouch_date, 
eng_vouchers_detail.purch_qty, 
eng_vouchers_detail.sale_qty, 
GREATEST(
eng_stock.supplier, 
eng_stock.customer 
) AS cust_sup, 
eng_stock.report_link 
FROM eng_stock 
LEFT JOIN 
eng_vouchers_detail 
ON eng_stock.doc_id = eng_vouchers_detail.doc_id 
WHERE eng_vouchers_detail.prod_id = 43 
ORDER BY vouch_date 

and here is result of this query

請幫我解決這個問題

Answer 1

試試這個：

SELECT 
eng_stock.doc_id, 
eng_vouchers_detail.prod_id, 
GREATEST(
    eng_stock.purch_date, 
    eng_stock.sale_date 
) AS vouch_date, 
eng_vouchers_detail.purch_qty, 
eng_vouchers_detail.sale_qty, 
eng_stock.report_link, 
sum(eng_vouchers_detail.purch_qty) AS p_sum, 
sum(eng_vouchers_detail.sale_qty) AS s_sum 
FROM 
    eng_stock 
LEFT JOIN eng_vouchers_detail ON eng_stock.doc_id = eng_vouchers_detail.doc_id 
    eng_vouchers_detail.prod_id = 43 
WHERE 
GROUP BY eng_stock.doc_id 
ORDER BY 
    vouch_date 

如果現在是你所需要的，請提供一些樣品你的表的數據。