php - Mysql在哪里计算

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 ?

我想要在哪里taa - tsa if 0显示查询请帮助我需要减法

我正在使用 WHERE taa-tsa = 0 但不起作用

我通过感谢解决了

Answer 1

如果要根据聚合值的内容过滤 SELECT 查询的输出，则需要在 HAVING 子句中指定过滤器(其中 WHERE 子句过滤输入行)。

因此:

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

您的查询结构非常糟糕。如果不了解更多有关数据结构、数据库和查询用法的信息，就不可能判断查询应该是什么样子。