存儲引擎
1）innodb
支持?jǐn)?shù)據(jù)庫高級功能：事務(wù)（要么整體成功要么整體失敗）外鍵
2）myisam
1.不支持事務(wù)页屠，外鍵粹胯，只有數(shù)據(jù)存儲基本功能
2.效率非常高

刪除數(shù)據(jù)庫

drop database if exists db1;

創(chuàng)建表

create table tb1(
 id int primary key auto_increment,
name varchar(20) not null,
num int not null unique,
xid int,
foreign key(xid) references tb2(id)
)engine=innodb charset=utf8;

更改表

-- 增加gender列
alter table tb1 add gender char(1) after name;

-- 設(shè)置字段為空

alter table tb1 modify num int null;

-- 設(shè)置自增

alter table tb1 modify id int auto_increment;

-- 去掉自增

alter table tb1 modify id int;

-- 刪除主鍵

alter table tb1 drop primary key;

-- 刪除外鍵

alter table tb1 drop foreign key (外鍵約束);

-- 刪除約束

alter table tb1 drop index 約束名;

-- 刪除表

drop table if exists tb1;

-- 查看安裝數(shù)據(jù)庫后的編碼
show variables like 'char%';
-- 運行結(jié)果

root@localhost:(none)>show variables like 'char%';
+--------------------------+---------------------------------------------------------+
| Variable_name            | Value                                                   |
+--------------------------+---------------------------------------------------------+
| character_set_client     | utf8                                                    |
| character_set_connection | utf8                                                    |
| character_set_database   | utf8                                                    |
| character_set_filesystem | binary                                                  |
| character_set_results    | utf8                                                    |
| character_set_server     | utf8                                                    |
| character_set_system     | utf8                                                    |
| character_sets_dir       | C:\Program Files\MySQL\MySQL Server 5.5\share\charsets\ |
+--------------------------+---------------------------------------------------------+
8 rows in set (0.00 sec)

-- 查看特定數(shù)據(jù)庫的編碼
show create database test;

root@localhost:test>show create database test;
+----------+---------------------------------------------------------------+
| Database | Create Database                                               |
+----------+---------------------------------------------------------------+
| test     | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER SET utf8 */ |
+----------+---------------------------------------------------------------+
1 row in set (0.00 sec)