SQL数据的增删改查:此部分所有SQL语句在navicat中与mysql命令行执行效果一样,只是mysql服务端在命令行执行,而navicat只是在客户端的图形化打开操作。
一、进入数据库
.连接数据库:mysql -uroot -p
.查看数据库:show databases;
.进入指定数据库:use test;
.查看表:show tables;
.查看当前用户名:select user();
.查看当前所在数据库:select database();
.修改字符集:set names ‘gbk‘;
.查看设计表:desc students;
.修改普通用户密码:update user set authentication_string=password(‘123456‘) where user=‘wzx‘;
flush privileges;
.忘记root用户密码:进入mysql的配置文件,找到my.ini的配置文件:
再[mysqld]下加入:skip-grant-tables后再重新启动mysql服务:
再进行连接测试:
.登录后记得删除配置文件并重新设置root密码:update user set authentication_string=password(‘123456‘) where user=‘wzx‘;
flush privileges;
.修改命令结束符:delimiter //?;
.查看设计表语句:show create table students;
.给表字段添加索引:create index name_index on students(name(255));
.开启运行时间监控:set profiling=1;
.查看监控结果:show profiles;
.查看表索引:show index from students;
注:主键、unique唯一值约束时默认会创建索引。一个表中的一个字段理论上可以有多个索引。
.删除表索引:drop index name_index on students;
.创建表数据时直接设置索引:
create table students(
id int primary key auto_increment ,
name varchar(10) not Null,
sex varchar(4) default "男",
age tinyint unsigned,
height decimal(5,2),
registration_time datetime
key (name)
);
二、创建数据库以及数据恢复与备份
.创建数据库:create database test0412 charset=‘utf8‘;
.删除数据库:drop database test0412;
.备份数据库:需要以管理员身份运行sql:mysqldump -uroot -p test > e:\test_back.sql;
.恢复数据:需要先创建数据库再导入数据库:
1:创建数据库:testback:create database testback charset=‘utf8‘;
2:导入数据库:mysql -uroot -p testback < e:\test_back.sql
三、创建表
1.1:直接创建新表
create table students(
id int primary key auto_increment ,
name varchar(10) not Null,
sex varchar(4) default "男",
age tinyint unsigned,
height decimal(5,2),
registration_time datetime
);
1.2:将需要备份数据表到新表
create table good_back select * from goods;
1.3:查询表数据后添加到新表
create table good_cate(
id int primary key auto_increment ,
goods_name varchar(30)
) select distinct good as goods_name from goods;
1.4:添加外键关系到已有数据表:
#### alter table 从表 add foreign key (从表字段) references 主表(主表字段);
alter table goods add foreign key (brand_id) references goods_brand(brand_id);
1.5:删除外键:
#### alter table 从表 drop foreign key (从表字段);
alter table goods drop foreign key (brand_id);
1.6:数据表时添加外键:
create table goods(
id int primary key auto_increment ,
goods_id int,
foreign key(goods_id) references goods_brand(goods_id)
) ;
四、增加值
2.1:按照数据库中字段顺序插入
INSERT into students value(0,"aa","女",21,3,"2019-02-12");
2.2:按照自己指定指定字段顺序插入
INSERT into students(sex,name,height,registration_time,age) value("保密","wqww",123,"2017-02-2",21);
2.3:在设计表中添加字段并给予说明
alter table students add new varchar(20) COMMENT ‘用户名‘;
2.4:一次性插入多个记录
insert into students values (0,‘老夫3‘,20),(0,‘老夫4‘,20),(0,‘老夫5‘,20);
2.5:将查询结果插入:
insert into goos_cate(cate_name) select distinct cate from goods;
五、修改记录
3.1:静态数据修改
update students set name="明天会更高" where id=1;
3.2:动态数据修改
update students set age=age+20 where id=2;
3.3:表数据修改
update goods g inner join goods_cate c on g.cate=c.cate_name set g.cate=c.cate_id;
六、删除记录
delete from students where id=2;
七、删除表
drop table students1;
drop table if exists sutdents1;
八、查询
6.1:给字段起别名:select name as 姓名,age as 年龄 from students;
6.2:给表起别名:select s.name as 姓名,s.age as 年龄 from students as s;
6.3:去重:select distinct age,class from students;
6.4:逻辑运算:select * from students where not name=‘王昭君‘;
6.5:模糊查询所有字符:select * from students where name like ‘王%‘;
6.6:模糊查询指定字符个数:select * from students where name like ‘王__‘;
6.7:范围查询:select * from students where age between 18 and 20;
6.8:为空:select * from students where sex is null;
6.9:为空字符:select * from students where sex=‘ ‘;
6.10:多字段排序:select * from students order by age desc,studentNo asc;
6.11:聚合函数:select count(*) as 学生总数 from students;
6.12:分组:select sex,count(*) from students group by sex;
6.13:分组后过滤having:select sex,count(*) from students group by sex having sex=‘男‘;
十、连接查询
1、等值连接,默认会形成笛卡尔积,需要条件过滤
select * from courses,scores where courses.courseno=scores.courseno;
2、内连接
select sc.score,cs.name from scores sc inner join courses cs on sc.courseno=cs.courseno
3、左连接
select stu.name,sc.score from students stu left join scores sc on stu.studentno=sc.studentno;
4、右链接
select sc.score,cs.name from scores sc right join courses cs on sc.studentno=cs.courseno
5、自关联
select * from areas p,areas c where p.aid=c.pid and p.atitle=‘河南省‘;
十一、子查询
6、标量子查询(一行一列的数据,一般是聚合函数)
select * from students where age > (select avg(age) from students);
7、列级子查询(一列多行的数据)
select * from students where name in (select name from students where hometown like ‘北京%‘);
8、行级子查询(一行多列的数据)
select * from students where (sex,age)=(select sex,age from students where sex=‘男‘ order by age desc limit 1);
9、表级子查询(多行多列)
十二、navicat操作
.表清空:删除所有数据,不删表结构,自动递增的值继续累加
.表截断:删除所有数据,不删表结构,自动递增的值从1开始
.备份:右键点击数据库-->存储sql文件
.恢复:右键点击数据库-->运行sql文件
.注释 ctrl + /
.取消注释 ctrl + shift + /
。查询mysql日志功能是否开启:show variables like‘general%‘;
。开启mysql日志功能:set global general_log=1;
.关闭mysql日志功能:set global general_log=0;