Question

如何以2％的价格适当提高饮料类产品的价格。这些表位于https://northwinddatabase.codeplex.com/ Northwind（SQL）数据库

中

我的非工作查询：

UPDATE products
SET unitprice = unitprice * 1.02
FROM products, categories
WHERE categories.categoryID = products.categoriesID
AND categories.categoryname LIKE '%Beverages'
GROUP BY products.categoryID;

Answer 1

不需要GROUP BY：

UPDATE p
    SET price = price * 1.02
    FROM products p JOIN
         categories c
         ON c.categoryID = p.categoriesID
    WHERE c.description LIKE '%Beverages';

如果多个类别可以匹配单个产品，则上述内容仍然只会将值增加2％（而不是每次匹配2％）。不过，我建议EXISTS而不是JOIN：

UPDATE p
    SET price = price * 1.02
    FROM products p JOIN
    WHERE EXISTS (SELECT 1
                  FROM categories c
                  WHERE c.categoryID = p.categoriesID AND
                        c.description LIKE '%Beverages'
                 );

如何使用两个表IN SQL在一个表中提高值？

1 个答案: