SQL查询小案例

这是一篇自学MySQL的小案例，下面是部分数据信息：goods表

1、查询cate_name为‘超级本’的商品名称、价格

SELECT
`name`,
price
FROM
goods
WHERE cate_name like '超级本';

-- 2、查询商品的种类

SELECT
cate_name
FROM
goods
GROUP BY
cate_name;

-- 3、查询所有电脑产品的平均价格，并且保留两位小数

SELECT
ROUND(avg(price), 2) AS avg_price
FROM
goods;

-- 4、查询每种商品的平均价格

SELECT
cate_name,
avg(price) AS avg_price
FROM
goods
GROUP BY
cate_name;

-- 5、查询每种商品中的最高价格、最低价格，平均价、数量

SELECT
cate_name,
MAX(price) AS ma_price,
MIN(price) AS mi_price,
avg(price) AS avg_price,
COUNT(*)
FROM
goods
GROUP BY
cate_name;

-- 6、查询所有价格大于平均价格的商品、并且按价格降序排列

SELECT
id,
NAME,
cate_name,
brand_name,
price
FROM
goods
WHERE
price > (
SELECT
ROUND(AVG(price), 2)
FROM
goods
)
ORDER BY
price DESC;

-- 7、查询每种类型中最贵的电脑信息

SELECT
*
FROM
goods
INNER JOIN (
SELECT
cate_name,
MAX(price) AS max_price,
MIN(price) AS min_price,
COUNT(*)
FROM
goods
GROUP BY
cate_name
) AS goods_new_info ON goods.cate_name = goods_new_info.cate_name
AND goods.price = goods_new_info.max_price;