根據條件更新聲明

Question

如何更新DB中的discount_price價格 我需要根據自己的情況爲現有價值增加價值 示例：任何產品的價格從10到30 我必須向其中添加1.5。

產品，15應該是16.5例如

我寫了這個查詢

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

但我發現這個錯誤>>

SQL錯誤：

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，並且想要統計更新所影響的行數。

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中沒有對應的語法：如果是這樣，你可以使用一個可更新的CTE。