day03
一数据导入
二数据导出
三管理表记录 *
3.1 插入表记录
3.2 查询表记录 （单表 多表 嵌套 连接）
3.3 条件匹配
3.4 更新表记录字段的值
3.5 删除表记录
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一数据导入 : 把系统文件的内容存储到数据库的表里。
把系统已有的用户信息存储到studb.user表
/etc/passwd
用户名 密码站位符 uid gid 描述信息 家目录 shell
create database studb;
create table studb.user(
name char(50),
password char(1),
uid int(2),
gid int(2),
comment varchar(100),
homedir char(150),
shell char(50),
index(name)
);
查看导入数据时，搜索系统的目录
show variables like "secure_file_priv";
secure_file_priv | /var/lib/mysql-files/
mysql> load data infile "目录名/文件名" INTO TABLE 库.表
FIELDS TERMINATED BY "列间隔符号"
LINES TERMINATED BY "行间隔符号";
mysql> system cp /etc/passwd /var/lib/mysql-files/
mysql> load data
INFILE "/var/lib/mysql-files/passwd" INTO TABLE studb.user
FIELDS TERMINATED BY ":"
LINES TERMINATED BY "\n";
mysql>alter table studb.user add id int(2) primary key auto_increment first;
select * from studb.user;
++++++++++++++++++++++++++++++++++
修改导入数据时，搜索文件的目录 ？
#vim /etc/my.cnf
[mysqld]
secure_file_priv="/mydatadir"
......
:wq
#mkdir /mydatadir
#chown mysql /mydatadir
#setenforce 0
#systemctl start mysqld
#mysql -uroot -p123456
mysql> show variables like "secure_file_priv";
+------------------+-------------+
| Variable_name | Value |
+------------------+-------------+
| secure_file_priv | /mydatadir/ |
+------------------+-------------+
++++++++++++++++++++++++++++++++++
二数据导出: 把表记录存储到系统文件里。
mysql> show variables like "secure_file_priv";
MySQL> sql查询 INTO OUTFILE "目录名/文件名"；
MySQL> sql查询 INTO OUTFILE "目录名/文件名" FIELDS TERMINATED BY "列间隔符号" LINES TERMINATED BY "行间隔符号"；
select * from studb.user into outfile "/mydatadir/user1.txt";
system cat /mydatadir/user1.txt
select name,uid from studb.user into outfile "/mydatadir/user2.txt";
select name,uid from studb.user limit 3 ;
select name,uid from studb.user limit 3 into outfile "/mydatadir/user1.txt" fields terminated by "#";
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三管理表记录 * (增 删 改 查)
3.1 增 插入表记录
一次插入1条记录给所有字段赋值
insert into 库.表 values（值列表）；
insert into user values (51,"jim","x",2001,2001,"my student","/home/jim","/bin/bash");
一次插入多条记录给所有字段赋值
insert into 库.表 values（值列表），（值列表）；
insert into user values (52,"jim","x",2001,2001,"my student","/home/jim","/bin/bash"),(53,"jim","x",2001,2001,"my student","/home/jim","/bin/bash");
一次插入1条记录给指定字段赋值
insert into 库.表(字段名列表) values（值列表）；
insert into user(name,uid,gid) values("bob",3001,3001);
一次插入多条记录给指定字段赋值
insert into 库.表(字段名列表) values（值列表）,（值列表）；
insert into user(name,uid,gid) values("bob",3001,3001),("bob",3002,3001);
insert into user(name,password,uid,gid,comment,homedir,shell) values("plj","x",10000,10000,"teacher","/home/plj","/bin/bash");
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3.2 查询表记录 （单表 多表 嵌套 连接）
单表查询
select 字段名列表 from 库.表；
select 字段名列表 from 库.表 where 匹配条件；
select * from studb.user;
select id,name,homedir from studb.user;
select id,name,homedir from studb.user where id<=10;
select id,name,homedir from studb.user where name="root";
3.3 匹配条件 的 表示方式？
数值比较 = != > >= < <=
where 字段名 符号 数值
select name from user where uid=500;
select name from user where id<=10;
字符比较 = !=
where 字段名 符号 "字符串"
select name from user where shell="/bin/bash";
select name from user where name="daemon";
select name,shell from user where shell != "/bin/bash";
范围内匹配
where 字段名 between 值1 and 值2; 在...之间
where 字段名 in (值列表); 在....里
where 字段名 not in (值列表); 不在....里
select name,uid from user where uid between 10 and 20;
select name from user where name in ("root","lucy","damon");
select name,uid from user where uid in (100,500,1000,2001);
select name from user where shell not in ("/bin/bash","/sbin/nologin");
select name,shell from user where shell not in ("/bin/bash","/sbin/nologin");
逻辑匹配 （多个查询条件时 使用）
逻辑与 and 条件都成立才可以
逻辑或 or 某一个条件成立就可以
逻辑非 ！ 取反
select name from user where uid=10 and shell="/bin/bash" ;
select name,uid,shell from user where uid=0 and shell="/bin/bash" ;
select name from user where name="lucy" or name="bob" or uid=1;
select name,uid from user where name!="lucy";
匹配空 is null
匹配非空 is not null
select id ,name from user where name is null;
select id ,name from user where shell is null;
select id ,name,shell from user where shell is null;
select name ,shell from user where shell is not null;
insert into user(id,name)values(61,""),(62,null),(63,"null");
select id,name from user where name="";
select id,name from user where name is null;
select id,name from user where name="null";
DISTINCT 查询时，字段的重复值不显示，只显示第1次出现的值。
select shell from user;
select distinct shell from user;
select shell from user where uid <=1000;
select distinct shell from user where uid <=1000;
查询时做运算操作 + - / %
alter table user add s_year year default 2000 after name;
select from user;
select name , 2018 - s_year as age from user where name="root";
select name,uid,gid from user where name="bin";
select name,uid,gid, uid+gid as sum, (uid+gid)/2 as avg from user where name="bin";
select name,uid,gid, uid+gid as sum, (uid+gid)/2 as avg from user;
模糊查询 like
where 字段名 like '表达式';
% 表示零个或多个字符
_ 表示 一个字符
select id, name from user where name like '%';
select name from user where name like '%a%';
select name from user where name like '_'；
select name from user where name like '%_';
select name from user where name like '%__';
正则匹配
. ^ $ [ ] *
where 字段名 regexp '正则表达式'；
insert into user(name) values("yaya9"),("6yaya"),("ya5ya"),("y7aya");
select name from user where name regexp '[0-9]';
select name from user where name regexp '^[0-9]';
select name,uid from user where uid regexp '....';
select name,uid from user where uid regexp '^....$'
select name,uid from user where name regexp 'a.b';
select name,uid from user where name regexp '^r.t$';
统计函数（对字段的值做统计）
sum(字段)求和
avg(字段)求平均值
max(字段)求最大值
min(字段) 求最小值
count(字段) 统计个数
select avg(uid) from user where sex="girl";
select avg(uid) ,sum(uid) from user;
select min(uid),max(uid) from user;
select count(id) from user;
select count(name) from user;
select count(name),count(id) from user;
select count(name) from user where uid >1000;
查询结果分组
sql查询 group by 字段名；
select shell from user where uid<=100 ;
select shell from user where uid<=100 group by shell;
select distinct shell from user where uid<=100;
查询结果排序
sql查询 order by 字段名 asc/desc;
select uid,name from user where uid >=10 and uid<=100;
select uid,name from user where uid >=10 and uid<=100 order by uid;
select uid,name from user where uid >=10 and uid<=100 order by uid desc;
查询结果限制显示记录行数
sql查询 limit 数字；显示查询结果的前几行；
select id,name,uid,shell from user where id<=10 limit 1;
select id,name,uid,shell from user where id<=10 limit 3;
sql查询 limit 数字1，数字2；显示指定范围内的行
数字1 表示起始行 第1行的编号是 0
数字2 表示总行数
select id,name,uid,shell from user where id<=10；
select id,name,uid,shell from user where id<=10 limit 2,3;
select id,name,uid,shell from user where id<=10 limit 4,5;
select id,name,uid,shell from user where id<=10 limit 1,1;
select id,name,uid,shell from user where id<=10 limit 2;
查询表记录的语法格式：
select 字段名列表 from 库.表 where 匹配条件；
条件匹配：
数值比较 = != > >= < <=
字符比较 = !=
逻辑比较 and or !
范围内匹配 between...and \ in \ not in
空 is null
非空 is not null
模糊查询 like '表达式' % _
正则匹配 regexp '正则表达式' . ^ $ []
数学计算 + - / % ( )
统计函数 sum() avg() max() min() count()
不显示字段的重复值 distinct 字段名
查询分组 group by 字段名
查询排序 order by 字段名 asc/desc
限制显示查询记录的行数 limit 数字；
limit 数字1，数字2； limit 0,1
limit 2,2
++++++++++++++++++++++++++++++++++++++++++++
3.4 更新表记录字段的值 （条件和查询时的一样）
批量修改：
update 库.表 set 字段名=值,字段名="值"；
只修改复合条件记录字段的值：
update 库.表 set 字段名=值,字段名="值" where 条件；
update studb.user set s_year=1995 ;
update studb.user set s_year=1990 where name="root";
update studb.user set uid=uid+5 where uid<10;
update studb.user set uid=null where name="bin";
update studb.user set name="" where uid=5;
++++++++++++++++++++++++++++++
3.5 删除表记录 (条件和查询时的一样）
删除全部表记录 delete from 库.表；
删除指定的记录
delete from 库.表 where 条件；
delete from studb.user where uid is null;
+++++++++++++++++++++++++++++++++++++
where嵌套:把内层查询结果作为外查询的查询条件
select 字段名列表 from 库.表
where 条件 (select 字段名列表 from 库.表 where 条件);
alter table user add liunxsys float(5,2) default 60 after name;
update user set liunxsys=90 where uid=11;
update user set liunxsys=13 where uid=20;
update user set liunxsys=29 where uid=32;
select avg(liunxsys) from user where uid>=10 and uid<=50;
select name ,liunxsys from user where uid>=10 and uid<=50 and liunxsys < avg(liunxsys) ;
select name ,liunxsys from user where uid>=10 and uid<=50 and liunxsys < (select avg(liunxsys) from user where uid>=10 and uid<=50);
select name ,liunxsys from user where liunxsys < (select avg(liunxsys) from user);
select name from studb.user where name in (select user from mysql.user where host="localhost" and user="root");
stuinfo: name iphone class
addrinfo: name addr
select name from stuinfo where name in (select name from addrinfo where addr="beijing");
select name from stuinfo where name not in (select name from addrinfo where name="zhsan" and addr="beijing");
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复制表 ：
命令格式 create table 库.表 sql查询；
功能 1 快速创建新表 2 备份表
create table studb.user2 select * from studb.user;
create table studb.user3 select * from studb.user order by uid desc limit 5;
create database db4;
create table db4.user5 select * from studb.user where 1 = 2;
key值没有 要自己添加
++++++++++++++++++++++++++++++++++++++++++++++
对象 ： 学生 安娜
唯一标识学号
缴费表 110
班级表 110
就业表 110
多表 查询 -----SQL命令格式
select 字段名列表 from 表名列表; （迪卡尔集）
select 字段名列表 from 表名列表 where 条件；只显示与条件匹配的记录。
create database db4;
create table db4.t1 select name,uid,shell from studb.user limit 3;
create table db4.t2 select name,uid,homedir from studb.user limit 5;
select from db4.t1; select from db4.t2;
use db4;
select * from t1,t2; 3x5=15
select t1.name,t1.uid,t2.homedir from t1,t2; 3x5=15
select t1.name,t1.uid,t2.homedir from t1,t2 where t1.name = t2.name;
select t1.*,t2.homedir from t1,t2 where t1.name = t2.name and t1.uid = t2.uid;
连接查询
左连接查询
select 字段名列表 from 表A left join 表B on 条件；
右连接查询
select 字段名列表 from 表A right join 表B on 条件；
create table db4.t3 select name,uid,shell from studb.user limit 3;
create table db4.t4 select name,uid,shell from studb.user limit 5;
select from db4.t3; select from db4.t4;
select * from t3 left join t4 on t3.uid = t4.uid;
select * from t3 right join t4 on t3.uid = t4.uid;
mysql> select t3.shell from t3 left join t4 on t3.uid = t4.uid
-> group by shell;
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视图 存储过程 触发器
本文转自sweak_h 51CTO博客，原文链接：http://blog.51cto.com/13478354/2064355，如需转载请自行联系原作者
