简单查询语句

1 mysql> create table shop(id int(4) not null auto_increment,
2     -> name varchar(30),price double(15,2),sort varchar(20),
3     -> count int(5) default 0 not null,
4     -> primary key (id,name));
5 Query OK, 0 rows affected (0.15 sec)

 1 mysql> alter table shop
 2     -> add supplier_name varchar(50) not null default ‘tmall‘
 3     -> after price;
输出：
 4 Query OK, 5 rows affected (0.35 sec)
 5 Records: 5  Duplicates: 0  Warnings: 0
查看表变化：
 7 mysql> select * from shop;
 8 +----+-------+--------+---------------+------+-------+
 9 | id | name  | price  | supplier_name | sort | count |
10 +----+-------+--------+---------------+------+-------+
11 |  1 | apple |   2.50 | tmall         | A    |   500 |
12 |  2 | BOOK  |   2.40 | tmall         | B    |   500 |
13 |  3 | rule  |   1.20 | tmall         | B    |   200 |
14 |  4 | grape |   8.50 | tmall         | A    |   500 |
15 |  5 | pen   | 108.50 | tmall         | B    |    80 |
16 +----+-------+--------+---------------+------+-------+
17 5 rows in set (0.00 sec)

1 mysql> insert into shop values
2     -> (1,‘apple‘,2.50,‘A‘,500),
3     -> (2,‘BOOK‘,2.40,‘B‘,500),
4     -> (3,‘rule‘,1.20,‘B‘,200);
输出：
5 Query OK, 3 rows affected (0.08 sec)
6 Records: 3  Duplicates: 0  Warnings: 0

1 mysql> select max(price) as price,max(id) as id from shop;
输出：不可以按记录输出...
2 +-------+------+
3 | price | id   |
4 +-------+------+
5 |  2.50 |    3 |
6 +-------+------+
7 1 row in set (0.00 sec)

1 mysql> select * from shop where price =(select max(price) from shop);
输出：
2 +----+-------+-------+------+-------+
3 | id | name  | price | sort | count |
4 +----+-------+-------+------+-------+
5 |  1 | apple |  2.50 | A    |   500 |
6 +----+-------+-------+------+-------+
7 1 row in set (0.02 sec)

1 mysql> select * from shop order by price desc limit 1;
输出：
2 +----+-------+-------+------+-------+
3 | id | name  | price | sort | count |
4 +----+-------+-------+------+-------+
5 |  1 | apple |  2.50 | A    |   500 |
6 +----+-------+-------+------+-------+
7 1 row in set (0.00 sec)

 1 mysql> select * from shop;
 2 +----+-------+--------+---------------+------+-------+
 3 | id | name  | price  | supplier_name | sort | count |
 4 +----+-------+--------+---------------+------+-------+
 5 |  1 | apple |   2.50 | dangdang      | A    |   500 |
 6 |  2 | book  |   2.40 | tmall         | B    |   500 |
 7 |  3 | book  |   1.20 | jd            | B    |   200 |
 8 |  4 | apple |   8.50 | tmall         | A    |   500 |
 9 |  5 | pen   | 108.50 | jd            | B    |    80 |
10 +----+-------+--------+---------------+------+-------+
11 5 rows in set (0.00 sec)
12 
13 mysql> select supplier_name,sort,name,max(price) as price from shop group by sort,name;
14 输出：
15 +---------------+------+-------+--------+
16 | supplier_name | sort | name  | price  |
17 +---------------+------+-------+--------+
18 | dangdang      | A    | apple |   8.50 |
19 | tmall         | B    | book  |   2.40 |
20 | jd            | B    | pen   | 108.50 |
21 +---------------+------+-------+--------+
22 3 rows in set (0.00 sec)