MySQL第三课
首先创建一个数据库：
CREATE DATABASE ku;
Query OK, 1 row affected
查看一下是否有此数据库：
SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| ku |
| mysql |
| performance_schema |
| test |
+--------------------+
5 rows in set
使用此数据库：
USE ku;
Database changed
创建数据表：
CREATE TABLE biao(
name VARCHAR(20),
age INT(11),
sex CHAR(11),
love VARCHAR(11)
);
Query OK, 0 rows affected
查看表结构：
DESC biao;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| name | varchar(20) | YES | | NULL | |
| age | int(11) | YES | | NULL | |
| sex | char(11) | YES | | NULL | |
| love | varchar(11) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
4 rows in set
修改表名：
ALTER TABLE biao RENAME biao1;
Query OK, 0 rows affected
修改字段和类型：
ALTER TABLE biao1 CHANGE SEX SEX1 CHAR(20);
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
用圆括号！！！！
再查看一边：
DESC biao1;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| name | varchar(20) | YES | | NULL | |
| age | int(11) | YES | | NULL | |
| SEX1 | char(20) | YES | | NULL | |
| love | varchar(11) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
4 rows in set
修改字段的排列位置：
ALTER TABLE biao1 MODIFY NAME VARCHAR(20) AFTER SEX1;
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
查看：
DESC biao1;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| age | int(11) | YES | | NULL | |
| SEX1 | char(20) | YES | | NULL | |
| NAME | varchar(20) | YES | | NULL | |
| love | varchar(11) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
4 rows in set
注意改的是大写出现的也是大写
加一个think字段：
ALTER TABLE biao1 ADD think VARCHAR (10) AFTER LOVE;
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
查看：
DESC biao1;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| age | int(11) | YES | | NULL | |
| SEX1 | char(20) | YES | | NULL | |
| NAME | varchar(20) | YES | | NULL | |
| love | varchar(11) | YES | | NULL | |
| think | varchar(10) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
5 rows in set
删除think：
ALTER TABLE biao1 DROP think;
Query OK, 0 rows affected
Records: 0 Duplicates: 0 Warnings: 0
查看：
DESC biao1;
+-------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| age | int(11) | YES | | NULL | |
| SEX1 | char(20) | YES | | NULL | |
| NAME | varchar(20) | YES | | NULL | |
| love | varchar(11) | YES | | NULL | |
+-------+-------------+------+-----+---------+-------+
4 rows in set
删除此表：
DROP TABLE biao1;
Query OK, 0 rows affected
查看：
SHOW TABLES;
Empty set
删除数据库：
DROP DATABASE ku;
Query OK, 0 rows affected
查看：
SHOW DATABASES;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
4 rows in set
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