Mysql的計算在哪裏

Question

SELECT id as bid,sku,product_name, 
     (SELECT SUM(piece) FROM sales WHERE uid = bid) as tsa, 
     (SELECT SUM(piece) FROM buying WHERE uid = bid) as taa 
FROM product WHERE ? 

我想在那裏taa - tsa if 0節目查詢請幫助我需要減法

我使用WHERE taa-tsa = 0但不工作

我具有感謝解決

Answer 1

如果你想過濾一個SELECT查詢的輸出基於聚合值的內容，那麼你需要在HAVING子句中指定過濾器（WHERE子句用於過濾輸入行）。

因此可以：

SELECT id as bid,sku,product_name, 
    (SELECT SUM(piece) FROM sales WHERE uid = bid) as tsa, 
    (SELECT SUM(piece) FROM buying WHERE uid = bid) as taa 
FROM product 
HAVING tsa=taa 

或

SELECT ilv.* 
FROM (
    SELECT id as bid,sku,product_name, 
    (SELECT SUM(piece) FROM sales WHERE uid = bid) as tsa, 
    (SELECT SUM(piece) FROM buying WHERE uid = bid) as taa 
    FROM product 
) as ilv 
WHERE tsa=taa 

您的查詢非常糟糕構造。在不知道更多關於數據結構，數據庫和查詢用法的情況下，無法確定查詢應該是什麼樣子。

Answer 2

試試這個：

SELECT * FROM (
    SELECT id as bid,sku,product_name, 
      (SELECT SUM(piece) FROM sales WHERE uid = bid) as tsa, 
      (SELECT SUM(piece) FROM buying WHERE uid = bid) as taa 
    FROM product 
) as vw 

WHERE (vw.taa - vw.tsa) = 0