数据导入、导出、管理表记录、

数据导入: 把系统文件的内容存储到数据库服务器的表里
load data infile “目录名/文件名” into table 库名.表名
FIELDS TERMINATED BY “分隔符” LINES TERMINATED

BY “ ”;

load data infile "/etc/passwd" into table userdb.user

fields terminated by ":" lines terminated by " ";

例子：把系统用户信息存储到数据库服务器的表里
/etc/passwd
用户名:密码站位符号:uid:gid:描述信息:家目录:shell

create database userdb;
create table userdb.user(
name varchar(35),
password char(1),
uid int(2),
gid int(2),
comment varchar(60),
homedir varchar(60),
shell varchar(30),
index(name)
);

mysql> show variables like "secure_file_priv";

#cp /etc/passwd /var/lib/mysql-files/

mysql > load data infile "/var/lib/mysql-files/passwd"

into table userdb.user fields terminated by ":"

lines terminated by " ";

mysql> alter table userdb.user add id int(2) zerofill

primary key auto_increment first;

自定义数据导入时文件所在的目录
#mkdir /mydata
#chown mysql /mydata
#setenforce 0
#cp /etc/passwd /mydata/
vim /etc/my.cnf
[mysqld]
secure_file_priv= /mydata
:wq
#systemctl restart mysqld

数据导出:把表记录存储到系统文件里
mysql> show variables like "secure_file_priv";

sql查询命令 INTO OUTFILE “目录名/文件名“;

sql查询命令 INTO OUTFILE “目录名/文件名“ fields

terminated by "符号" lines terminated by "符号";

mysql>select * from userdb.user where id=18 into

outfile "/var/lib/mysql-files/user1.txt";

mysql> system cat /var/lib/mysql-files/user1.txt
++++++++++++++++++++++++++++++++++
管理表记录(增 查 改 删)（userdb.user）
insert into 增加表记录

一次插入1条记录给所有字段赋值
insert into 库名.表名 values(值列表);

一次插入N条记录给所有字段赋值
insert into 库名.表名 values(值列表),(值列表),(值列表);

插入记录时只给指定的字段赋值
insert into 库名.表名(字段名列表)values(值列表);
insert into 库名.表名(字段名列表)values(值列表),(值列表),(

值列表);

insert into userdb.user values

(50,"bob","x",2022,2022,"this is

student","/home/bob","/bin/bash");

insert into userdb.user values

(60,"bob","x",2122,2122,"this is

student","/home/bob","/bin/bash"),

(63,"lucy","x",2322,2322,"this is

student","/home/lucy","/bin/bash");

insert into userdb.user(name,uid)values("tom",2300),

("alic",2987);

insert into userdb.user

(name,password,uid,gid,comment,homedir,shell)

values

("yaya","x",3003,3003,"teacher","/home/yaya","/bin/ba

sh");

select 查询表记录
单表查询
查询表中所有记录所有字段的值
select * from 库.表 ；

查询表中所有记录指定字段的值
select 字段名列表 from 库.表 ；

查询表中符合条件记录指定字段的值
select 字段名列表 from 库.表 where 条件；

查询条件的表示方式？
1 数值比较 > >= < <= = !=
字段名 符号 数字
select name,uid from userdb.user where uid<10;
select * from userdb.user where id<=5;

2 字符比较 = ！=
字段名 符号 “字符串”
select name from userdb.user where name="apache";
select name from userdb.user where shell="/bin/bash";

select name,shell,uid from userdb.user where

shell="/bin/bash";

select name from userdb.user where name!="root";

3 范围内查找
in (值列表) 在...里
not in (值列表) 不在...里
between....and... 在...之间

select name from userdb.user where uid in (10,20,30);

select id,name from userdb.user where name in (

"mysql","rysnc","bob");

select name from userdb.user where shell not in

("/bin/bash","/sbin/nologin");

select name,shell,uid from userdb.user where shell not

in ("/bin/bash","/sbin/nologin");

select name,uid from userdb.user where uid between

10 and 20;

select id,name,uid from userdb.user where id between

30 and 40;

多个查询条件
逻辑与 and 多个查询条件必须同时成立
逻辑或 or 多个查询条件某一个条件成立就可以
逻辑非 ！ 取反

select name from userdb.user where name="apache"

and uid=1200 and shell="/bin/bash";

select name from userdb.user where name="apache"

or uid=2 or shell="/bin/bash";

select name,uid,shell from userdb.user where

name="apache" or uid=2 or shell="/bin/bash";

select name,uid from userdb.user
where
name="root" or name="bin" and uid=1;

select name,uid from userdb.user
where
name="root" and name="bin" or uid=1;

select name,uid from userdb.user
where
(name="root" or name="bin" ) and uid=2;

select name,uid from userdb.user
where
(name="root" or name="bin" ) and uid=1;

DISTINCT 不显示重复的值
select distinct shell from userdb.user;
select distinct shell from userdb.user where

uid<1000;

is null 匹配空
is not null 匹配非空
insert into userdb.user(id ,name)values(66,NULL),

(67,null),(68,"null"),(69,"");

select id , name from userdb.user where name is null;
select id , name from userdb.user where name is not

null;

select id , name from userdb.user where name="null";
select id , name from userdb.user where name="";

四则运算 + - * / %
alter table userdb.user
add linuxsys tinyint(2) default 60 after name,
add linuxser tinyint(2) default 80 after linuxsys;

alter table userdb.user
add age tinyint(2) unsigned default 20 after name;

select name,linuxsys,linuxser from userdb.user;

select name,linuxsys,linuxser from userdb.user where

name="root";

select name,linuxsys,linuxser,linuxsys+linuxser as zcj

from userdb.user where name="root";

select name,linuxsys,linuxser,linuxsys+linuxser as zcj,

(linuxsys+linuxser)/2 as pjf from userdb.user where

name="root";

select name,age from userdb.user where name="root";

select name,age,2017-age as s_year from userdb.user

where name="root";

聚集函数（做数据统计的内置命令）
sum(字段名) 求和
avg(字段名) 平均值
min(字段名) 最小值
max(字段名) 最大值
count(字段名) 个数

select sum(linuxsys) ,avg(linuxsys) from userdb.user;

select sum(linuxsys) ,avg(linuxsys) from userdb.user
-> where
-> uid<=10;

select min(uid) from userdb.user where

shell="/bin/bash";

select max(uid) from userdb.user where

shell="/bin/bash";

select count(id) ,count(name) from userdb.user;

select count(name) from userdb.user where

shell="/bin/bash";

模糊匹配
like ‘表达式’
% 零个或多个字符
_ 任意单个字符

select name from userdb.user where name like '____';

select name,uid from userdb.user
where name like '%a%';

select name,uid from userdb.user
where name like 'a%';

select id,name,uid from userdb.user
where name like '%';

select id,name,uid from userdb.user
where name like '_a_';

select id,name,uid from userdb.user
where name like 'r__t';

select id,name,uid from userdb.user
where uid like '____';

select id,name,uid from userdb.user
where uid like '%_%';

select name,id from userdb.user where name like '%_%'

and name="";

select name,uid from userdb.user where name like

'____' and uid>=1000;

正则匹配
regexp '正则表达式'
^ $ . * []

insert into userdb.user(id , name)values(71,"yaya3"),

(72,"9yaya"),(73,"ya7ya"),(74,"yay6a");

select name from userdb.user
where
name regexp '[0-9]';

select name from userdb.user
where
name regexp '^[0-9]';

select name from userdb.user
where
name regexp '[0-9]$';

select name from userdb.user
where
name regexp '.....';

select name from userdb.user
where
name regexp '^.....$';

select name,uid from userdb.user
where
uid regexp '...';

select name,uid from userdb.user
where
uid regexp '^...$';

insert into userdb.user(id ,name)values(80,"ro");

select id,name,uid from userdb.user
where name regexp '^r.*o$';

select id,name,uid from userdb.user
where name regexp '.*';

限制显示查询记录数
limit 数字 显示查询结果的前几行

limit 起始行,总行数
起始行的编号从零开始

select * from userdb.user;
select * from userdb.user limit 3;
select * from userdb.user where uid <=10 limit 5;

select * from userdb.user limit 1,3;

mysql> select * from userdb.user where uid <=10

limit 2,3;

查询排序
order by 字段名 asc/desc

select name,uid,shell from userdb.user where shell!

="/bin/bash" and shell is not null order by uid;

select name,uid,shell from userdb.user where shell!

="/bin/bash" and shell is not null order by uid desc;

select name,uid,shell from userdb.user where shell!

="/bin/bash" and shell is not null order by uid desc

limt 3;

select name,uid,shell from userdb.user where shell!

="/bin/bash" and shell is not null order by uid limit

5;

select 姓名，工资 from yginfo where age<=30 and 部门

="ope" order by 工资 desc;

查询分组
group by 字段名；

select shell from userdb.user where uid>=10 and

uid<=40 ;

select shell from userdb.user where uid>=10 and

uid<=40 group by shell;

select gid from userdb.user group by gid;

select shell from userdb.user group by shell;

select gid from userdb.user group by gid having gid=1;

update修改表记录（修改记录字段的值）
批量修改
update 库.表 set 字段名="值"，字段名=值；
update userdb.user set linuxser=100,linuxsys=80;

修改与条件匹配的记录字段的值；
update 库.表 set 字段名="值"，字段名=值 where 条件；
update userdb.user set age=18 where name="root";

update userdb.user set shell=null where name="bin";
update userdb.user set shell="" where name="root";

delete删除表记录(以行为单位删除)
删除表的所有记录
delete from 库.表；

删除表中与条件匹配的记录
delete from 库.表 where 条件；
delete from userdb.user where shell is null;

where嵌套查询（把内层的查询结果作为外层查询的查询条件）
select 字段名列表 from 库.表 where 条件 （select 字段名列

表 from 库.表）；

update userdb.user set linuxsys=93 where uid>=10

and uid<=50;

select name,linuxsys from userdb.user where linuxsys

< (select avg(linuxsys) from userdb.user);

select name,linuxsys from userdb.user where linuxsys

> (select avg(linuxsys) from userdb.user);

select name from userdb.user where name in (select

user from mysql.user where user="root" and

host="localhost");
+++++++++++++++++++++++++++++++++++++++++++++
复制表
作用： 1 快速创建新表
2 备份表
create table 库.表 sql查询命令；

create table userdb.user2 select * from userdb.user;

create table userdb.user3 select * from userdb.user

where 1 = 2;

create table userdb.top5user select * from

userdb.user order by uid desc limit 5;

create database teadb;
create table teadb.t1 select name,uid,homedir from

userdb.user where uid<=10;
select * from teadb.t1;

多表查询
select 字段名列表 from 表名列表；
select 字段名列表 from 表名列表 where 条件；

use teadb;
create table t2 select name,uid,homedir from userdb.user limit 3;

create table t3 select name,uid,shell from userdb.user limit 5;

3 x 5 15
select * from t2,t3; 笛卡尔集
select t2.* ,t3.name from t2,t3;

select t2.name,t3.name from t2,t3 where t2.name=t3.name;

select t2.name,t2.homedir,t3.name,t3.shell from t2,t3 where t2.name=t3.name;

连接查询
左连接查询:以左边的表为主显示查询记录
select 字段名列表 from 表名 left join 表名 on 条件；
右连接查询:以右边的表为主显示查询记录
select 字段名列表 from 表名 right join 表名 on 条件；
use tead;
create table t4 select name,uid,shell from userdb.user limit 3;
create table t5 select name,uid,shell from userdb.user limit 5;
select * from t4 left join t5 on t4.uid = t5.uid;
select * from t4 right join t5 on t4.uid = t5.uid;