mysql轻快入门（3）

有一种情况，你忘记数据库密码啦，你怎么办，砸电脑吗？no..... 请见下： select host,user,password from mysql.user; update mysql.user set password=password('123') where name='root';

grant select,insert,update,delete on cissst.* to guest@localhost identified by '123';//这个一般在发布的时候创建一个低级别的账号供用户使用，即创建一个 //guest本地用户 密码123,对数据库cissit下的表有select,update,delete权限

(1)windows下 强行重置mysql root密码： step1:net stop mysql step2:mysqld --skip-grant-tables 启动mysql服务，但不加载权限检查 step3:再开个窗口输入mysql回车进入mysql 界面 step4:update mysql.user set password=password('mysql') where name='root'; step5:\q step6:update mysql.user set password=password('123') where name='root'; C:\Documents and Settings\Administrator>netstat -nao |find "3306" TCP 0.0.0.0:3306 0.0.0.0:0 LISTENING 328 TCP 127.0.0.1:1059 127.0.0.1:3306 TIME_WAIT 0

step7:taskkill -f -pid 328 step8:net start mysql step9:mysql -uroot -pmysql 完成

（2）linux下差不多 step1:pkill mysql&& pkill mysqld step2:mysqld --skip-grant-tables 启动mysql服务，但不加载权限检查 step3:再开个窗口输入mysql回车进入mysql 界面 step4:update mysql.user set password=password('mysql') where name='root'; step5:\q step6:update mysql.user set password=password('123') where name='root'; step 7 :ps aux|grep mysql && pkill mysqld 然后启动mysql即可

备份： C:\>mysqldump -uroot -pmysql cissst >c:\cissst.sql

还原： 创建一个待还原的新数据库： sql>create database cissst; \q c:>mysql -uroot -pmysql cissst <c:\cissst.sql windows和liuux差不多

（char）举例

mysql> create table t5(f1 char(4),f2 varchar(4)); Query OK, 0 rows affected (0.16 sec)

mysql> desc t5; +-------+------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+------------+------+-----+---------+-------+ | f1 | char(4) | YES | | NULL | | | f2 | varchar(4) | YES | | NULL | | +-------+------------+------+-----+---------+-------+ 2 rows in set (0.00 sec)

mysql> insert into t5 values('hi ','hi '); Query OK, 1 row affected, 1 warning (0.05 sec)

mysql> select length(f1),length(f2) from t5; +------------+------------+ | length(f1) | length(f2) | +------------+------------+ | 2 | 4 | +------------+------------+ 1 row in set (0.03 sec)

mysql> select concat(f1,'+'),concat(f1,'+') from t5; +----------------+----------------+ | concat(f1,'+') | concat(f1,'+') | +----------------+----------------+ | hi+ | hi+ | +----------------+----------------+ 1 row in set (0.00 sec)

mysql> select concat(f1,'+'),concat(f2,'+') from t5; +----------------+----------------+ | concat(f1,'+') | concat(f2,'+') | +----------------+----------------+ | hi+ | hi + | +----------------+----------------+ 1 row in set (0.00 sec) 总结：从上面可以看出char与varchar的区别 1.(char)一个定长，不够用空格填充，取出来会去掉右边的空格,因此如果后边本身有的空格便会没有了，但varchar不会，varchar空间利用率更高一些，但并非100%,他还会有一些指示字符串长度的一些东西，但定长速度快

(int) mysql>create table t1(f1 int,f2 int(3)); Query OK, 0 rows affected (0.22 sec)

mysql> desc t1; +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | f1 | int(11) | YES | | NULL | | | f2 | int(3) | YES | | NULL | | +-------+---------+------+-----+---------+-------+ 2 rows in set (0.03 sec)

mysql> insert into t1 values(1002100010,1234); Query OK, 1 row affected (0.03 sec)

mysql> select *from t1; +------------+------+ | f1 | f2 | +------------+------+ | 1002100010 | 1234 | +------------+------+ 1 row in set (0.03 sec)

mysql> create table t2(f1 int unsigned zerofill); Query OK, 0 rows affected (0.08 sec)

mysql> desc t2; +-------+---------------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------------------------+------+-----+---------+-------+ | f1 | int(10) unsigned zerofill | YES | | NULL | | +-------+---------------------------+------+-----+---------+-------+ 1 row in set (0.00 sec)

mysql> insert into t2 values(12); Query OK, 1 row affected (0.03 sec)

mysql> select *from t2; +------------+ | f1 | +------------+ | 0000000012 | +------------+ 1 row in set (0.00 sec)

mysql> insert into t2 values(-12); ERROR 1264 (22003): Out of range value adjusted for column 'f1' at row 1 mysql> create table t3(id int not null auto_increment primary key); Query OK, 0 rows affected (0.11 sec)

mysql> desc t3; +-------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | +-------+---------+------+-----+---------+----------------+ 1 row in set (0.02 sec)

mysql> create table t4(id int zerofill); Query OK, 0 rows affected (0.09 sec)

mysql> desc t4; +-------+---------------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------------------------+------+-----+---------+-------+ | id | int(10) unsigned zerofill | YES | | NULL | | +-------+---------------------------+---- 总结：（1）unsigend无符号 （2）int(M) zerofill 只有zerofill写了M才有意义，zerofill默认unsigned

（date)

create table t6(f1 date,f2 datetime,f3 timestamp);

Query OK, 0 rows affected (0.08 sec)

mysql> desc t6; +-------+-----------+------+-----+-------------------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-----------+------+-----+-------------------+-------+ | f1 | date | YES | | NULL | | | f2 | datetime | YES | | NULL | | | f3 | timestamp | NO | | CURRENT_TIMESTAMP | | +-------+-----------+------+-----+-------------------+-------+ 3 rows in set (0.02 sec)

mysql> insert into t6(f1,f2) values('1983-01-02','1986-03-01 12:10:11'); Query OK, 1 row affected (0.05 sec)

mysql> select *from t6; +------------+---------------------+---------------------+ | f1 | f2 | f3 | +------------+---------------------+---------------------+ | 1983-01-02 | 1986-03-01 12:10:11 | 2014-11-16 09:42:48 | +------------+---------------------+---------------------+ 1 row in set (0.00 sec)

mysql> insert into t6 values(now(),now(),null); Query OK, 1 row affected, 1 warning (0.06 sec)

mysql> select *from t6; +------------+---------------------+---------------------+ | f1 | f2 | f3 | +------------+---------------------+---------------------+ | 1983-01-02 | 1986-03-01 12:10:11 | 2014-11-16 09:42:48 | | 2014-11-16 | 2014-11-16 09:44:11 | 2014-11-16 09:44:11 | +------------+---------------------+---------------------+ 2 rows in set (0.00 sec)

mysql> show variables like 'time_zone'; +---------------+--------+ | Variable_name | Value | +---------------+--------+ | time_zone | SYSTEM | +---------------+--------+ 1 row in set (0.00 sec)

mysql> set time_zone='+9:00'; Query OK, 0 rows affected (0.02 sec)

mysql> select *from t6; +------------+---------------------+---------------------+ | f1 | f2 | f3 | +------------+---------------------+---------------------+ | 1983-01-02 | 1986-03-01 12:10:11 | 2014-11-16 10:42:48 | | 2014-11-16 | 2014-11-16 09:44:11 | 2014-11-16 10:44:11 | +------------+---------------------+---------------------+ 2 rows in set (0.00 sec)

mysql> create table t7(sex enum('M','F') default 'M'); Query OK, 0 rows affected (0.08 sec)

mysql> insert into t7 values('m'),(null),(1); Query OK, 3 rows affected (0.03 sec) Records: 3 Duplicates: 0 Warnings: 0

mysql> select * from t7; +------+ | sex | +------+ | M | | NULL | | M | +------+ 3 rows in set (0.00 sec)

mysql> select 9>7; +-----+ | 9>7 | +-----+ | 1 | +-----+ 1 row in set (0.00 sec) 总结： timestamp 不需要手动填值，它自动获取当前时间，并且时区改变，也会影响它的值，如上，查看时区可以用show variables like 'time_zone'; 设置时区用set time_zone='+9:00

 编码

 mysql> \s

mysql Ver 14.12 Distrib 5.0.83, for Win32 (ia32)

Connection id: 1 Current database: Current user: root@localhost SSL: Not in use Using delimiter: ; Server version: 5.0.83-community-nt MySQL Community Edition (GPL) Protocol version: 10 Connection: localhost via TCP/IP Server characterset: gbk Db characterset: gbk Client characterset: gbk Conn. characterset: gbk TCP port: 3306 Uptime: 9 sec

Threads: 1 Questions: 4 Slow queries: 0 Opens: 12 Flush tables: 1 Open tabl es: 6 Queries per second avg: 0.444 修改编码及校对集 alter database demo character set gbk; alter table t5 character set gbk; alter tablet t5 modify f1 char(4) character set gbk; alter table t1 modify f1 varchar(20) collate=gbk_bin; 可以用下面的命令查看支持的校对集 slect COLLATION_NAME,CHARACTER_SET_NAME where CHARACTER_SET_NAME like '%gbk%';