Question

我查找了几种通过SELECT更新多列的方法，但仍然无法使其工作。这就是我试过的：

delimiter @@
CREATE TRIGGER trigger_sales 
AFTER INSERT ON orders
FOR EACH ROW
BEGIN
UPDATE sales 
SET (userid, productid, transaction, price, quarter) =
SELECT userid, productid, COUNT(productid) AS transaction, SUM(total_P) AS price,
       case when (month(date)) >=3 and (month(date)) <=5 then 'Spring' 
            when (month(date)) >=6 and (month(date)) <=8 then 'Summer'
            when (month(date)) >=9 and (month(date)) <=11 then 'Fall' 
            else 'Winter'
            end AS quarter  
FROM orders     
GROUP BY userid, productid, quarter
END@@
delimiter;

谢谢！

Answer 1

我喜欢这样做的首选方法是执行INSERT查询，确保每个插入都有一个已经使用的主键。然后我添加ON DUPLICATE KEY UPDATE，浏览`column`=VALUES(`column`)形式的所有字段，这样就可以了。这通常适用于外键。

Answer 2

我在没有任何样本数据的情况下测试了您的查询，但此解决方案可以让您走上正确的轨道。我在多个表格上使用VIEW时使用GROUP BY来克服UPDATE限制：

CREATE VIEW orders_view AS
     SELECT userid, 
            productid, 
            COUNT(productid) AS 'transaction', 
            SUM(total_P) AS price,
            CASE 
       WHEN (MONTH(o.date)) >=3 AND (MONTH(o.date)) <=5 THEN 'Spring' 
       WHEN (MONTH(o.date)) >=6 AND (MONTH(o.date)) <=8 THEN 'Summer'
       WHEN (MONTH(o.date)) >=9 AND (MONTH(o.date)) <=11 THEN 'Fall'
               ELSE 'Winter'
            END AS quarter    
       FROM orders     
   GROUP BY userid, productid, quarter;

     UPDATE sales s, orders_view o
        SET s.userid = o.userid,
            s.productid = o.productid,
            s.`transaction` = o.`transaction`,
            s.price = o.price,
            s.quarter = o.quarter
      WHERE s.userid = o.userid;

请注意，我没有使用真实数据对其进行测试。

更多信息：

MySQL参考手册：UPDATE Syntax

如何在MYSQL中一次更新多个列？

2 个答案: