s_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('PowerEdge T110 II服务器','服务器/工作站','戴尔','5388',DEFAULT,DEFAULT);
INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('Mac Pro MD878CH/A 专业级台式电脑','服务器/工作站','苹果','28888',DEFAULT,DEFAULT);
INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES(' HMZ-T3W 头戴显示设备','笔记本配件','索尼','6999',DEFAULT,DEFAULT);
INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('商务双肩背包','笔记本配件','索尼','99',DEFAULT,DEFAULT);
INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('X3250 M4机架式服务器 2583i14','服务器/工作站','IBM','6888',DEFAULT,DEFAULT);
INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('玄龙精英版 笔记本散热器','笔记本配件','九州风神','',DEFAULT,DEFAULT);
INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES(' HMZ-T3W 头戴显示设备','笔记本配件','索尼','6999',DEFAULT,DEFAULT);
INSERT tdb_goods (goods_name,goods_cate,brand_name,goods_price,is_show,is_saleoff) VALUES('商务双肩背包','笔记本配件','索尼','99',DEFAULT,DEFAULT);
-- 求所有电脑产品的平均价格,并且保留两位小数，AVG,MAX,MIN、COUNT、SUM为聚合函数
SELECT ROUND(AVG(goods_price),2) AS avg_price FROM tdb_goods;
-- 查询所有价格大于平均价格的商品，并且按价格降序排序
SELECT goods_id,goods_name,goods_price FROM tdb_goods WHERE goods_price > 5845.10 ORDER BY goods_price DESC;
-- 使用子查询来实现
SELECT goods_id,goods_name,goods_price FROM tdb_goods
WHERE goods_price > (SELECT ROUND(AVG(goods_price),2) AS avg_price FROM tdb_goods)
ORDER BY goods_price DESC;
-- 查询类型为“超记本”的商品价格
SELECT goods_price FROM tdb_goods WHERE goods_cate = '超级本';
-- 查询价格大于或等于"超级本"价格的商品，并且按价格降序排列
SELECT goods_id,goods_name,goods_price FROM tdb_goods
WHERE goods_price = ANY(SELECT goods_price FROM tdb_goods WHERE goods_cate = '超级本')
ORDER BY goods_price DESC;
-- = ANY 或 = SOME 等价于 IN
SELECT goods_id,goods_name,goods_price FROM tdb_goods
WHERE goods_price IN (SELECT goods_price FROM tdb_goods WHERE goods_cate = '超级本')
ORDER BY goods_price DESC;
-- 创建“商品分类”表
CREATE TABLE IF NOT EXISTS tdb_goods_cates(
cate_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
cate_name VARCHAR(40)
);
-- 查询tdb_goods表的所有记录，并且按"类别"分组
SELECT goods_cate FROM tdb_goods GROUP BY goods_cate;
-- 将分组结果写入到tdb_goods_cates数据表
INSERT tdb_goods_cates (cate_name) SELECT goods_cate FROM tdb_goods GROUP BY goods_cate;
-- 通过tdb_goods_cates数据表来更新tdb_goods表
UPDATE tdb_goods INNER JOIN tdb_goods_cates ON goods_cate = cate_name
SET goods_cate = cate_id ;
-- 通过CREATE...SELECT来创建数据表并且同时写入记录
-- SELECT brand_name FROM tdb_goods GROUP BY brand_name;
CREATE TABLE tdb_goods_brands (
brand_id SMALLINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
brand_name VARCHAR(40) NOT NULL
) SELECT brand_name FROM tdb_goods GROUP BY brand_name;
-- 通过tdb_goods_brands数据表来更新tdb_goods数据表(错误)
UPDATE tdb_goods INNER JOIN tdb_goods_brands ON brand_name = brand_name
SET brand_name = brand_id;
-- Column 'brand_name' in field list is ambigous
-- 正确
UPDATE tdb_goods AS g INNER JOIN tdb_goods_brands AS b ON g.brand_name = b.brand_name
SET g.brand_name = b.brand_id;
-- 查看tdb_goods的数据表结构
DESC tdb_goods;
-- 通过ALTER TABLE语句修改数据表结构
ALTER TA |