MySQL第六次作业
作业3：视图
mysql> create database vw;
mysql> use vw;
mysql> create table Student(
-> Sno int primary key,
-> Sname varchar(20),
-> Ssex varchar(20),
-> Sage int,
-> Sdept varchar(20));
mysql> create table Course(
-> Cno int primary key,
-> Cname varchar(20));
mysql> create table SC( Sno int, Cno int , Score int,primary key(Sno,Cno));
Query OK, 0 rows affected (0.00 sec)
mysql> desc SC;
+-------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+---------+------+-----+---------+-------+
| Sno | int(11) | NO | PRI | NULL | |
| Cno | int(11) | NO | PRI | NULL | |
| Score | int(11) | YES | | NULL | |
+-------+---------+------+-----+---------+-------+
3 rows in set (0.00 sec)
mysql> select * from Student;
+-----+-------+------+------+---------+
| Sno | Sname | Ssex | Sage | Sdept |
+-----+-------+------+------+---------+
| 1 | xixi | M | 12 | chinese |
| 2 | mama | F | 23 | english |
| 3 | lala | M | 34 | chinese |
+-----+-------+------+------+---------+
3 rows in set (0.00 sec)
mysql> select * from Course;
+-----+-------+
| Cno | Cname |
+-----+-------+
| 1 | mysql |
| 2 | java |
| 3 | k8s |
+-----+-------+
3 rows in set (0.00 sec)
mysql> select * from SC;
+-----+-----+-------+
| Sno | Cno | Score |
+-----+-----+-------+
| 1 | 1 | 66 |
| 1 | 3 | 89 |
| 2 | 1 | 78 |
| 2 | 2 | 90 |
| 2 | 3 | 88 |
| 3 | 1 | 67 |
| 3 | 2 | 89 |
+-----+-----+-------+
7 rows in set (0.00 sec)
mysql> create view stu_info (name,sex,cname,score) AS select Sname,Ssex,Cname,Scoore from Student s,Course c,SC a where s.Sno=a.Sno and c.Cno=a.Cno;
Query OK, 0 rows affected (0.00 sec)
mysql> select * from stu_info;
+------+------+-------+-------+
| name | sex | cname | score |
+------+------+-------+-------+
| xixi | M | mysql | 66 |
| mama | F | mysql | 78 |
| lala | M | mysql | 67 |
| mama | F | java | 90 |
| lala | M | java | 89 |
| xixi | M | k8s | 89 |
| mama | F | k8s | 88 |
+------+------+-------+-------+
7 rows in set (0.00 sec)
mysql> drop view stu_info;
Query OK, 0 rows affected (0.00 sec)
作业2索引
create table goods( goods_id int(11) primary key auto_increment, goods__name varchar(20) not null, cat_id int(11) not null default 0, brand_id int(11) not null default 0, goods_sn char(12) not null, shop_price float(6,2) not null default 0.00, goods_desc text default null)engine=myisam charset=utf8mb4 collate=utf8mb4_general_ci;
二、索引
1、建立一个utf8编码的数据库test1
2、建立商品表goods和栏目表category
按如下表结构创建表：存储引擎engine myisam 字符集charset utf8
mysql> desc goods;
+------------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+----------------+
| goods_id | int(11) | NO | PRI | NULL | auto_increment |
| goods_name | varchar(20) | NO | | | |
| cat_id | int(11) | NO | | 0 | |
| brand_id | int(11) | NO | | 0 | |
| goods_sn | char(12) | NO | | | |
| shop_price | float(6,2) | NO | | 0.00 | |
| goods_desc | text | YES | | NULL | |
+------------+-------------+------+-----+---------+----------------+
7 rows in set (0.00 sec)
mysql> desc category;
+-----------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-------------+------+-----+---------+----------------+
| cat_id | int(11) | NO | PRI | NULL | auto_increment |
| cate_name | varchar(20) | NO | | | |
| parent_id | int(11) | NO | | 0 | |
+-----------+-------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)
3、删除 goods 表中的 goods_desc 字段及货号字段,并增加 click_count 字段
mysql> alter table goods drop goods_desc;
mysql> alter table goods drop brand_id ;
mysql> alter table goods add click_count int(11);
mysql> desc goods;
+-------------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+-------------+------+-----+---------+----------------+
| goods_id | int(11) | NO | PRI | NULL | auto_increment |
| goods__name | varchar(20) | NO | | NULL | |
| cat_id | int(11) | NO | | 0 | |
| goods_sn | char(12) | NO | | NULL | |
| shop_price | float(6,2) | NO | | 0.00 | |
| click_count | int(11) | YES | | NULL | |
+-------------+-------------+------+-----+---------+----------------+
6 rows in set (0.00 sec)
4、在 goods_name 列上加唯一性索引（用alter table方式）
5、在 shop_price 列上加普通索引（用create index方式）
mysql> create index index2 on goods(shop_price);
mysql> alter table goods add unique index index1 (goods__name);
mysql> mysql> show index from goods;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| goods | 0 | PRIMARY | 1 | goods_id | A | 0 | NULL | NULL | | BTREE | | |
| goods | 0 | index1 | 1 | goods__name | A | 0 | NULL | NULL | | BTREE | | |
| goods | 1 | index2 | 1 | shop_price | A | NULL | NULL | NULL | | BTREE | | |
6、在 click_count 上增加普通索引，然后再删除 （分别使用drop index和alter table删除）
mysql> alter table goods add index index3 (click_count);
mysql> drop index index3 on goods;
Query OK, 0 rows affected (0.00 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> show index from goods;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| goods | 0 | PRIMARY | 1 | goods_id | A | 0 | NULL | NULL | | BTREE | | |
| goods | 0 | index1 | 1 | goods__name | A | 0 | NULL | NULL | | BTREE | | |
| goods | 1 | index2 | 1 | shop_price | A | NULL | NULL | NULL | | BTREE | | |
mysql> alter table goods add index index4 (click_count);
mysql> show index from goods;
| goods | 0 | PRIMARY | 1 | goods_id | A | 0 | NULL | NULL | | BTREE | | |
| goods | 0 | index1 | 1 | goods__name | A | 0 | NULL | NULL | | BTREE | | |
| goods | 1 | index2 | 1 | shop_price | A | NULL | NULL | NULL | | BTREE | | |
| goods | 1 | index4 | 1 | click_count | A | NULL | NULL | NULL | YES | BTREE | | |
mysql> alter table goods drop index index4;
mysql> show index from goods;
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| goods | 0 | PRIMARY | 1 | goods_id | A | 0 | NULL | NULL | | BTREE | | |
| goods | 0 | index1 | 1 | goods__name | A | 0 | NULL | NULL | | BTREE | | |
| goods | 1 | index2 | 1 | shop_price | A | NULL | NULL | NULL | | BTREE | | |