表操作

储引擎：即表的类型，不同的引擎处理机制不同

查看mysql支持的存储引擎

show engines;

 +--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+

创建表指定表类型（存储引擎）

mysql> create table t1(id int) engine=innodb;#对应两张表t1.frm t1.ibd

mysql> create table t2(id int) engine=memory;#数据存放与内存，只有结构表，无数据表t2.frm

mysql> create table t3(id int) engine=blackhome;#数据黑洞，只有结构表，无数据表t3.frm

mysql> create table t4(id int) engine=myisam;#对于3张表t4.frm t4.MYD t4.MYI

创建表 

create table t5(
    -> id int,
    -> name varchar(50),
    -> sex enum('male','female'),
    -> age int(13)
    -> );

mysql> desc t5;
+-------+-----------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+-----------------------+------+-----+---------+-------+
| id | int(11) | YES | | NULL | |
| name | varchar(50) | YES | | NULL | |
| sex | enum('male','female') | YES | | NULL | |
| age | int(13) | YES | | NULL | |
+-------+-----------------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

查看详细信息

show create table t5G

修改表结构 

修改表名：

　　alter table 表明 rename 新表明;

增加字段：

alter table 表名 add 字段名 数据类型 [完整性约束]

alter table 表名 add 字段名 数据类型 [完整性约束] first

alter table 表名 add 字段名 数据类型 [完整性约束] after 字段名

删除字段：

alter table 表名drop 字段名

修改字段：

alter table 表名 modify 字段名

alter table 表名 change 原字段名 新字段名 数据类型

复制表

复制表结构+数据 

#创建新的数据库
mysql> create database db3;
#切换数据库
mysql> use db3;
#复制mysql.user表中的host,user字段到新表t1中
mysql> create table t1 select host,user from mysql.user;
Query OK, 4 rows affected (0.01 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> desc t1;

+-------+----------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| host | char(60) | NO | | | |
| user | char(32) | NO | | | |
+-------+----------+------+-----+---------+-------+
2 rows in set (0.00 sec)

复制表结构

#添加一个不存在的条件即可拷贝表结构
create table t2 select host,user from mysql.user where host="123"; 

拷贝整张表结构 

create table t3 like mysql.user;

 删除表

drop table t1;

清空表

delete from 表名; 用于和where连用删除指定数据行

主：delete无法清空auto_increment记录，下次增加不会从1开始自增。

truncate 表明;清空表所有信息。