根据条件更新声明

Question

如何更新DB中的discount_price价格 我需要根据自己的情况为现有价值增加价值 示例：任何产品的价格从10到30 我必须向其中添加1.5。

产品，15应该是16.5例如

我写了这个查询

UPDATE products 
    SET discount_price = discount_price + 1.5 
    WHERE discount_price >= 10 AND discount_price <= 30; 

但我发现这个错误>>

SQL错误：

ERROR: syntax error at or near "SET" 
LINE 1: SELECT COUNT(*) AS total FROM (UPDATE products SET discount_... 
                ^
In statement: 
SELECT COUNT(*) AS total FROM (UPDATE products SET discount_price = discount_price + 1.5 
WHERE discount_price >= 10 AND discount_price <=30) AS sub 

Answer 1

我猜你正在使用Postgres，并且想要统计更新所影响的行数。

WITH p as (
     UPDATE products 
      SET discount_price = discount_price + 1.5 
      WHERE discount_price >= 10 AND discount_price <= 30 
      RETURNING * 
    ) 
SELECT COUNT(*) 
FROM p; 

有MySQL中没有对应的语法：如果是这样，你可以使用一个可更新的CTE。