技術標籤：MySQLmysql聯結表

建立聯結

SELECT vend_name, prod_name, prod_price FROM vendors, products WHERE vendors.vend_id = products.vend_id;

WHERE子句的重要性

-- WHERE子句的重要性
-- 笛卡兒積（檢索出的行的數目是第一個表的行數乘以第二個表中的行數）
SELECT * FROM vendors;
SELECT * FROM products;
SELECT vend_name, prod_name, prod_price FROM vendors, products;
 

內聯結

SELECT * FROM vendors INNER JOIN products ON vendors.vend_id = products.vend_id;

聯結多個表

SELECT * FROM orderitems, products, vendors WHERE products.vend_id = vendors.vend_id AND orderitems.prod_id = products.prod_id AND order_num = 20007;