1.创建数据表
1>.调用数据库命令：USE itcast;
命令输入正确后的结果
Database changed ;
2>.创建时数据表：CREATE TABLE student_tb
-> (
-> id INT(10),
-> name CHAR(20),
-> age INT(2),
-> sex CHAR(5)
-> );
命令输入正确后的结果
Query OK, 0 rows affected
2.查看数据表是否创建成功：SHOW TABLES;
命令输入正确后的结果
+------------------+
| Tables_in_itcast |
+------------------+
| student_tb |
+------------------+
1 row in set
3.查看已创建数据表信息：SHOW CREATE TABLE student_tb;
命令输入正确后的结果
+------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| student_tb | CREATE TABLE `student_tb` (
`id` int(10) DEFAULT NULL,
`name` char(20) DEFAULT NULL,
`age` int(2) DEFAULT NULL,
`sex` char(5) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8 |
+------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set
4.查看数据表信息（表的具体信息）：DESC student_tb;
命令输入正确后的结果
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int(10) | YES | | NULL | |
| name | char(20) | YES | | NULL | |
| age | int(2) | YES | | NULL | |
| sex | char(5) | YES | | NULL | |
+-------+----------+------+-----+---------+-------+
4 rows in set
5.修改数据表名称：ALTER TABLE student_tb RENAME TO student1923_tb;
命令输入正确后的结果
Query OK, 0 rows affected
6.修改数据字段名：ALTER TABLE student1923_tb CHANGE name username CHAR(20);
命令输入正确后的结果
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
7.修改字段数据类型：ALTER TABLE student1923_tb MODIFY username VARCHAR(20);
命令输入正确后的结果
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
查看数据表信息（表的具体信息）是否修改成功:DESC student1923_tb;
命令输入正确后的结果
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id | int(10) | YES | | NULL | |
| username | varchar(20) | YES | | NULL | |
| age | int(2) | YES | | NULL | |
| sex | char(5) | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
4 rows in set
8.添加字段：
1>.添加至最后：ALTER TABLE student1923_tb ADD address CHAR(20);
命令输入正确后的结果
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
查看数据表信息（表的具体信息）是否修改成功:DESC student1923_tb;
命令输入正确后的结果
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id | int(10) | YES | | NULL | |
| username | varchar(20) | YES | | NULL | |
| age | int(2) | YES | | NULL | |
| sex | char(5) | YES | | NULL | |
| address | char(20) | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
5 rows in set
2>.添加至中间：ALTER TABLE student1923_tb ADD mail CHAR(30) AFTER sex;
命令输入正确后的结果
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
查看数据表信息（表的具体信息）是否修改成功:DESC student1923_tb;
命令输入正确后的结果
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| id | int(10) | YES | | NULL | |
| username | varchar(20) | YES | | NULL | |
| age | int(2) | YES | | NULL | |
| sex | char(5) | YES | | NULL | |
| mail | char(30) | YES | | NULL | |
| address | char(20) | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
6 rows in set
3>.添加至最前:ALTER TABLE student1923_tb ADD grade CHAR(30) FIRST;
命令输入正确后的结果
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
查看数据表信息（表的具体信息）是否修改成功:DESC student1923_tb;
命令输入正确后的结果
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| grade | char(30) | YES | | NULL | |
| id | int(10) | YES | | NULL | |
| username | varchar(20) | YES | | NULL | |
| age | int(2) | YES | | NULL | |
| sex | char(5) | YES | | NULL | |
| mail | char(30) | YES | | NULL | |
| address | char(20) | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
7 rows in set
9.删除字段：ALTER TABLE student1923_tb DROP mail;
命令输入正确后的结果
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
查看数据表信息（表的具体信息）是否修改成功:DESC student1923_tb;
命令输入正确后的结果
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| grade | char(30) | YES | | NULL | |
| id | int(10) | YES | | NULL | |
| username | varchar(20) | YES | | NULL | |
| age | int(2) | YES | | NULL | |
| sex | char(5) | YES | | NULL | |
| address | char(20) | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
6 rows in set
10.修改字段排列位置：
1>.将字段修改为第一：ALTER TABLE student1923_tb MODIFY username VARCHAR(20) FIRST;
命令输入正确后的结果
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
查看数据表信息（表的具体信息）是否修改成功:DESC student1923_tb;
命令输入正确后的结果
+----------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| username | varchar(20) | YES | | NULL | |
| grade | char(30) | YES | | NULL | |
| id | int(10) | YES | | NULL | |
| age | int(2) | YES | | NULL | |
| sex | char(5) | YES | | NULL | |
| address | char(20) | YES | | NULL | |
+----------+-------------+------+-----+---------+-------+
6 rows in set
2>.将字段修改为...后：ALTER TABLE student1923_tb MODIFY username VARCHAR(20) AFTER grade;
命令输入正确后的结果
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
11.删除数据表：DROP TABLE student1923_tb;
命令输入正确后的结果
Query OK, 0 rows affected
12.查看是否删除数据表成功：SHOW TABLES;
命令输入正确后的结果
Empty set
13.字键约束：
1>.单字段：CREATE TABLE exam1
-> (
-> id INT(20),
-> name CHAR(20) PRIMARY KEY
-> );
命令输入正确后的结果
Query OK, 0 rows affected
查看数据表信息（表的具体信息）是否修改成功:DESC exam1;
命令输入正确后的结果
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int(20) | YES | | NULL | |
| name | char(20) | NO | PRI | NULL | |
+-------+----------+------+-----+---------+-------+
2 rows in set
2>.多字段：CREATE TABLE exam2
-> (
-> id INT(20),
-> name CHAR(20),
-> PRIMARY KEY(id,name)
-> );
命令输入正确后的结果
Query OK, 0 rows affected
查看数据表信息（表的具体信息）是否修改成功:DESC exam2;
命令输入正确后的结果
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int(20) | NO | PRI | 0 | |
| name | char(20) | NO | PRI | | |
+-------+----------+------+-----+---------+-------+
2 rows in set
14.非空约束：CREATE TABLE exam3
-> (
-> id INT(20),
-> name CHAR(20) NOT NULL
-> );
命令输入正确后的结果
Query OK, 0 rows affected
查看数据表信息（表的具体信息）是否修改成功:DESC exam3;
命令输入正确后的结果
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int(20) | YES | | NULL | |
| name | char(20) | NO | | NULL | |
+-------+----------+------+-----+---------+-------+
2 rows in set
15.唯一约束：CREATE TABLE exam4
-> (
-> id INT(20),
-> name CHAR(20)UNIQUE
-> );
命令输入正确后的结果
Query OK, 0 rows affected
查看数据表信息（表的具体信息）是否修改成功：DESC exam４；
命令输入正确后的结果
+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id | int(20) | YES | | NULL | |
| name | char(20) | YES | UNI | NULL | |
+-------+----------+------+-----+---------+-------+
2 rows in set