创建表和索引

1、创建表，这里需要注意，5.5以后默认引擎是InnoDB，5.1及之前是MyIsam

mysql> create table student(
    -> id int(4) not null,
    -> name char(20) not null,
    -> age tinyint(2) not null default '0',
    -> dept varchar(16) default null
    -> );
Query OK, 0 rows affected (0.03 sec)


mysql> 
mysql> show create table student\G
*************************** 1. row ***************************
       Table: student
Create Table: CREATE TABLE `student` (
  `id` int(4) NOT NULL,
  `name` char(20) NOT NULL,
  `age` tinyint(2) NOT NULL DEFAULT '0',
  `dept` varchar(16) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)

mysql> 

2、创建带有主键和普通索引的表

mysql> create table student1(
    -> id int(4) not null auto_increment,
    -> name char(20) not null,
    -> age tinyint(2) not null default '0',
    -> dept varchar(16) default null,
    -> primary key (id),
    -> key index_name(name));
Query OK, 0 rows affected (0.11 sec)

mysql> desc student1
    -> ;
+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| id    | int(4)      | NO   | PRI | NULL    | auto_increment |
| name  | char(20)    | NO   | MUL | NULL    |                |
| age   | tinyint(2)  | NO   |     | 0       |                |
| dept  | varchar(16) | YES  |     | NULL    |                |
+-------+-------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

3、增加主键

mysql> alter table student change id id int primary key auto_increment;
Query OK, 0 rows affected (0.08 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc student
    -> ;
+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| id    | int(11)     | NO   | PRI | NULL    | auto_increment |
| name  | char(20)    | NO   |     | NULL    |                |
| age   | tinyint(2)  | NO   |     | 0       |                |
| dept  | varchar(16) | YES  |     | NULL    |                |
+-------+-------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> 

4、增加普通索引

mysql>  alter table student add index ind_name(name);
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc student;
+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| id    | int(11)     | NO   | PRI | NULL    | auto_increment |
| name  | char(20)    | NO   | MUL | NULL    |                |
| age   | tinyint(2)  | NO   |     | 0       |                |
| dept  | varchar(16) | YES  |     | NULL    |                |
+-------+-------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> 

5、增加具有长的普通索引

mysql> create index ind_dept on student(dept(8));
Query OK, 0 rows affected (0.29 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc student
    -> ;
+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| id    | int(11)     | NO   | PRI | NULL    | auto_increment |
| name  | char(20)    | NO   | MUL | NULL    |                |
| age   | tinyint(2)  | NO   |     | 0       |                |
| dept  | varchar(16) | YES  | MUL | NULL    |                |
+-------+-------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> 

6、查看表上有哪些索引

mysql> show index from student
    -> ;
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table   | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| student |          0 | PRIMARY  |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| student |          1 | ind_name |            1 | name        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| student |          1 | ind_dept |            1 | dept        | A         |           0 |        8 | NULL   | YES  | BTREE      |         |               |
+---------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
3 rows in set (0.00 sec)

mysql> 

7、创建组合索引

mysql> create index ind_name_age on student(name,age);
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> show index from student;
+---------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table   | Non_unique | Key_name     | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| student |          0 | PRIMARY      |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| student |          1 | ind_name     |            1 | name        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| student |          1 | ind_dept     |            1 | dept        | A         |           0 |        8 | NULL   | YES  | BTREE      |         |               |
| student |          1 | ind_name_age |            1 | name        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| student |          1 | ind_name_age |            2 | age         | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
+---------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
5 rows in set (0.00 sec)

mysql> 

8、创建唯一索引

mysql> create unique index uni_ind_age on student(age);
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc student;
+-------+-------------+------+-----+---------+----------------+
| Field | Type        | Null | Key | Default | Extra          |
+-------+-------------+------+-----+---------+----------------+
| id    | int(11)     | NO   | PRI | NULL    | auto_increment |
| name  | char(20)    | NO   | MUL | NULL    |                |
| age   | tinyint(2)  | NO   | UNI | 0       |                |
| dept  | varchar(16) | YES  | MUL | NULL    |                |
+-------+-------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> 
mysql> 
mysql> show index from student;
+---------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table   | Non_unique | Key_name     | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| student |          0 | PRIMARY      |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| student |          0 | uni_ind_age  |            1 | age         | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| student |          1 | ind_name     |            1 | name        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| student |          1 | ind_dept     |            1 | dept        | A         |           0 |        8 | NULL   | YES  | BTREE      |         |               |
| student |          1 | ind_name_age |            1 | name        | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| student |          1 | ind_name_age |            2 | age         | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
+---------+------------+--------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
6 rows in set (0.00 sec)

mysql>