使用子查询和连接优化进行查询

Question

不知何故我对我的查询语句不满意，想知道是否有其他更好的方法来做到这一点：

SELECT product.product, 
 COALESCE((SELECT SUM(qty) FROM stocktrxn 
 INNER JOIN stock on stock.tra_no = stocktrxn.tra_no 
 WHERE product_no = s1.product_no and stock.is_out = false) - 
 (SELECT SUM(qty) FROM stocktrxn 
 INNER JOIN stock on stock.tra_no = stocktrxn.tra_no 
 WHERE product_no = s1.product_no and stock.is_out = true), 0)
 as qty
FROM stocktrxn s1
RIGHT JOIN product on product.id = s1.product_no
GROUP BY product ASC;

Answer 1

我认为您只需要条件聚合。像这样：

SELECT p.product,
       (SUM(CASE WHEN s.is_out = false THEN qty ELSE 0 END) -
        SUM(CASE WHEN s.is_out = true THEN qty ELSE 0 END) -
       ) as qty
FROM product LEFT JOIN
     stocktrxn st
     ON p.id = st.product_no LEFT JOIN
     stock s
     ON s.tra_no = st.tra_n
GROUP BY p.product ASC;

使用子查询和连接优化进行查询

query using subquery and joins optimization

mysql

join

subquery