我正在尝试进行hw,但我不确定为什么我的代码显示空列。
说明:编写并运行SQL语句,该语句显示由未知供应商提供的产品的描述和价格(即,产品供应商未列在数据库中)。TIA!
我的代码
SELECT P_DESCRIPT AS "Product Description", P_PRICE "Price"
FROM PRODUCT P, VENDOR V
WHERE P.V_CODE = V.V_CODE and V.V_CODE is null;
使用左联接:
SELECT
P_DESCRIPT AS "Product Description",
P_PRICE "Price"
FROM PRODUCT P
LEFT JOIN VENDOR V
ON P.V_CODE = V.V_CODE
WHERE V.V_CODE IS NULL;