BLE tdb_goods
CHANGE goods_cate cate_id SMALLINT UNSIGNED NOT NULL,
CHANGE brand_name brand_id SMALLINT UNSIGNED NOT NULL;
-- 分别在tdb_goods_cates和tdb_goods_brands表插入记录
INSERT tdb_goods_cates(cate_name) VALUES('
路由器'),('
交换机'),('网卡');
INSERT tdb_goods_brands(brand_name) VALUES('海尔'),('清华同方'),('神舟');
-- 在tdb_goods数据表写入任意记录
INSERT tdb_goods(goods_name,cate_id,brand_id,goods_price) VALUES(' LaserJet Pro P1606dn 黑白激光打印机','12','4','1849');
-- 查询所有商品的详细信息(通过内连接实现)如下如：
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM tdb_goods AS g
INNER JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
INNER JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id\G;
-- 查询所有商品的详细信息(通过左外连接实现)
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM tdb_goods AS g
LEFT JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
LEFT JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id\G;
-- 查询所有商品的详细信息(通过右外连接实现)
SELECT goods_id,goods_name,cate_name,brand_name,goods_price FROM tdb_goods AS g
RIGHT JOIN tdb_goods_cates AS c ON g.cate_id = c.cate_id
RIGHT JOIN tdb_goods_brands AS b ON g.brand_id = b.brand_id\G;
-- 无限分类的数据表设计
CREATE TABLE tdb_goods_types(
type_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
type_name VARCHAR(20) NOT NULL,
parent_id SMALLINT UNSIGNED NOT NULL DEFAULT 0
);
INSERT tdb_goods_types(type_name,parent_id) VALUES('家用电器',DEFAULT);
INSERT tdb_goods_types(type_name,parent_id) VALUES('电脑、办公',DEFAULT);
INSERT tdb_goods_types(type_name,parent_id) VALUES('大家电',1);
INSERT tdb_goods_types(type_name,parent_id) VALUES('生活电器',1);
INSERT tdb_goods_types(type_name,parent_id) VALUES('平板电视',3);
INSERT tdb_goods_types(type_name,parent_id) VALUES('空调',3);
INSERT tdb_goods_types(type_name,parent_id) VALUES('电风扇',4);
INSERT tdb_goods_types(type_name,parent_id) VALUES('饮水机',4);
INSERT tdb_goods_types(type_name,parent_id) VALUES('电脑整机',2);
INSERT tdb_goods_types(type_name,parent_id) VALUES('电脑配件',2);
INSERT tdb_goods_types(type_name,parent_id) VALUES('笔记本',9);
INSERT tdb_goods_types(type_name,parent_id) VALUES('超级本',9);
INSERT tdb_goods_types(type_name,parent_id) VALUES('游戏本',9);
INSERT tdb_goods_types(type_name,parent_id) VALUES('CPU',10);
INSERT tdb_goods_types(type_name,parent_id) VALUES('主机',10);
-- 查找所有分类及其父类
SELECT s.type_id,s.type_name,p.type_name FROM tdb_goods_types AS s LEFT JOIN tdb_goods_types AS p ON s.parent_id = p.type_id;
-- 查找所有分类及其子类
SELECT p.type_id,p.type_name,s.type_name FROM tdb_goods_types AS p LEFT JOIN tdb_goods_types AS s ON s.parent_id = p.type_id;
-- 查找所有分类及其子类的数目
SELECT p.type_id,p.type_name,count(s.type_name) AS children_count FROM tdb_goods_types AS p LEFT JOIN tdb_goods_types AS s ON s.parent_id = p.type_id GROUP BY p.type_name ORDER BY p.type_id;
-- 为tdb_goods_types添加child_count字段
ALTER TABLE tdb_goods_types ADD child_count MEDIUMINT UNSIGNED NOT NULL DEFAULT 0;
-- 将刚才查询到的子类数量更新到tdb_goods_types数据表
UPDATE tdb_goods_types AS t1 INNER JOIN ( SELECT p.type_id,p.type_name,count(s.type_name) AS children_count FROM tdb_goods_types AS p
LEFT JOIN tdb_goods_types AS s ON s.parent_id = p.type_id
GROUP BY p.type_name
ORDER BY p.type_id ) AS t2
ON t1.type_id = t2.type_id
SET t1.child_count = t2.children_count;
-- 复制编号为12,20的两条记录
SELE |