MySql:在复杂的 if 语句中更改源表

Question

我不确定这是否可行。但我有以下 sql，它根据产品的特价向 product_filter 表插入一些值。

INSERT INTO product_filter (product_id,filter_id)
SELECT product_id,
  (CASE WHEN price < 100 then 1
  WHEN price >= 100 AND price < 500 then 2
  WHEN price >= 500 AND price < 1000 then 3
  WHEN price >= 1000 AND price < 1500 then 4
  WHEN price >= 1500 AND price < 2000 then 5
  WHEN price >= 2000 AND price < 2500 then 50
  WHEN price >= 2500 AND price < 3000 then 6
  ELSE 51 END) AS filter_id
FROM product_special;

我想修改上面的脚本，这样如果没有为产品设置特殊价格，它只会从主 product 表中读取常规价格。由于这将在大型产品数据库上运行，因此我希望可以组合这两个脚本，而不是在某些产品上手动运行不同的脚本。

感谢您的帮助。

Answer 1

INSERT INTO product_filter (product_id,filter_id)

  SELECT product_id,
  (CASE WHEN price < 100 then 1
  WHEN price >= 100 AND price < 500 then 2
  WHEN price >= 500 AND price < 1000 then 3
  WHEN price >= 1000 AND price < 1500 then 4
  WHEN price >= 1500 AND price < 2000 then 5
  WHEN price >= 2000 AND price < 2500 then 50
  WHEN price >= 2500 AND price < 3000 then 6
  ELSE 51 END) AS filter_id
  FROM product_special
  union
  SELECT product_id,
  (CASE WHEN price < 100 then 1
  WHEN price >= 100 AND price < 500 then 2
  WHEN price >= 500 AND price < 1000 then 3
  WHEN price >= 1000 AND price < 1500 then 4
  WHEN price >= 1500 AND price < 2000 then 5
  WHEN price >= 2000 AND price < 2500 then 50
  WHEN price >= 2500 AND price < 3000 then 6
  ELSE 51 END) AS filter_id
  FROM product where product_id not in
  (select product_id from product_special)

以上查询假设您有 product_id和price (作为标准/正常价格)product 中的列 table 。这里的想法是从 product_special 获取所有现有产品。表及其特价，并添加 product_special 中不存在的产品。表，但在 product 中表及其标准/常规价格。