标签：foreign log 显示 其他 ffffff inno offset 递增 优先级
desc （表名）t1； 查看表格信息内容 表的信息 show create table t1（表名）：也是查看信息，还不多是横向查看 show create table t1 \G; 竖向查看自增信息 alter table t1 AUTO_INCREMENT=3; 可以修改自增
show session variables like “auto_inc%；查看全局变量 set session auto_increment_increment=2; 设置绘画步长 set global auto_increment_offset=10; 表示自增长字段每次递增的量，其默认值是1;
show global variables like ‘auto_inc%‘; 查看全局变量 set global auto_increment_increment=2; 设置会话步长 # set global auto_increment_offset=10;
CREATE TABLE `t5` ( `nid` int(11) NOT NULL AUTO_INCREMENT, `pid` int(11) NOT NULL, `num` int(11) DEFAULT NULL, PRIMARY KEY (`nid`,`pid`) ) ENGINE=InnoDB AUTO_INCREMENT=4, 步长=2 DEFAULT CHARSET= =utf8 //设置步长 及自动增加
唯一索引：索引列的值必须唯一，但允许有空值。如果是组合索引，则列值的组合必须唯一。
主键索引：不允许有空值。一般是在建表的时候同时创建主键索引。
unique 唯一索引名称 (列名,列名)//联合索引, unique uq_u1 (user_id), //唯一索引
create table t1( id int ...., num int, xx int, unique 唯一索引名称 (列名,列名) //联合索引 constraint .... )
用户： 1 alex 1 2 root 1 3 egon 2 4 laoyao 3 部门: 1 服务 2 保安 3 公关 ===》 一对多
用户表： 1 alex 2 root 3 egon 4 laoyao 博客表： FK() + 唯一 1 /yuanchenqi/ 4 2 /alex3714/ 1 3 /asdfasdf/ 3 4 /ffffffff/ 2 ===> 一对一
create table userinfo1( id int auto_increment primary key, name char(10), gender char(10), email varchar(64) )engine=innodb default charset=utf8; create table admin( id int not null auto_increment primary key, username varchar(64) not null, password VARCHAR(64) not null, user_id int not null, unique uq_u1 (user_id), //唯一索引 CONSTRAINT fk_admin_u1 FOREIGN key (user_id) REFERENCES userinfo1(id) )engine=innodb default charset=utf8;
示例1： 用户表 相亲表 示例2： 用户表 主机表 用户主机关系表 ===》多对多 create table userinfo2( id int auto_increment primary key, name char(10), gender char(10), email varchar(64) )engine=innodb default charset=utf8; create table host( id int auto_increment primary key, hostname char(64) )engine=innodb default charset=utf8; create table user2host( id int auto_increment primary key, userid int not null, hostid int not null, unique uq_user_host (userid,hostid), //联合唯一 CONSTRAINT fk_u2h_user FOREIGN key (userid) REFERENCES userinfo2(id), CONSTRAINT fk_u2h_host FOREIGN key (hostid) REFERENCES host(id) )engine=innodb default charset=utf8;
create table tb12( id int auto_increment primary key, name varchar(32), age int )engine=innodb default charset=utf8;
insert into tb11(name,age) values(‘alex‘,12); //单行插入 insert into tb11(name,age) values(‘alex‘,12),(‘root‘,18); //多行插入 insert into tb12(name,age) select name,age from tb11; //将tb11里面表的内容插入tb12;
delete from tb12; delete from tb12 where id !=2 delete from tb12 where id =2 delete from tb12 where id > 2 delete from tb12 where id >=2 delete from tb12 where id >=2 or name=‘alex‘
update tb12 set name=‘alex‘ where id>12 and name=‘xx‘ update tb12 set name=‘alex‘,age=19 where id>12 and name=‘xx‘
select * from tb12; select id,name from tb12; select id,name from tb12 where id > 10 or name =‘xxx‘; select id,name as cname from tb12 where id > 10 or name =‘xxx‘; //as可以修改序列名； select name,age,11 from tb12; //查看另一张表
a:条件 select * from tb12 where id != 1 select * from tb12 where id in (1,5,12); //查看表id是1,5,12的 select * from tb12 where id not in (1,5,12);//查看表id不是1,5,12的 select * from tb12 where id in (select id from tb11) select * from tb12 where id between 5 and 12; //闭开间取范围的 b:通配符： select * from tb12 where name like "a%" // a开头的所有（%多个字符串） select * from tb12 where name like "a_" //a开头的（— 一个字符） c:限制（分页）： select * from tb12 limit 10; // 前10行 select * from tb12 limit 0,10; //从1行开始的10行 select * from tb12 limit 10,10; //从10行开始的10行 select * from tb12 limit 10 offset 20; //从第10行开始的20行 d：排序 select * from tb12 order by id desc; 大到小 select * from tb12 order by id asc; 小到大 select * from tb12 order by age desc,id desc; 优先级先第一个，如果数据相同在从第二个开始从大小排序 取后10条数据 （先排序在取数据） select * from tb12 order by id desc limit 10; e：分组：**** select count(id), part_id from userinfo5 group by part_id; count max min sum avg ******如果对于聚合函数结果进行第二次筛选时，必须使用having***** select count(id),part_id from userinfo5 group by part_id having count(id) > 1; select count(id),part_id from userinfo5 where id > 0 group by part_id having count(id) > 1; 特别的：group by 必须在where之后，order by之前 f:连表：******** select * from userinfo5 left join department5 on userinfo5.part_id = department5.id select * from department5 left join userinfo5 on userinfo5.part_id = department5.id //usernfo5 左边全部显示 //department5 左边全部显示 # select * from userinfo5 right join department5 on userinfo5.part_id = department5.id # department5右边全部显示 userinfo5表所有显示，如果department5中无对应关系，则值为null select * from userinfo5 innder join department5 on userinfo5.part_id = department5.id 将出现null时一行隐藏
标签：foreign log 显示 其他 ffffff inno offset 递增 优先级
原文地址：http://www.cnblogs.com/niejinmei/p/6953379.html
