Mac安装mysql数据库MySQL基础和MySQL在开发中常用的技术
一.安装步骤
打开终端，输入：
sudo vi ~/.bash_profile
输入 i
然后粘贴以下内容
# mysql
alias mysql='/usr/local/mysql/bin/mysql'
alias mysqladmin='/usr/local/mysql/bin/mysqladmin'
# ls
alias ls='ls -G'
按ESC键
输入 :wq
重新启动终端程序
在命令行中输入下面命令修改密码
mysqladmin -u root password "123456"
Last login: Sun Nov 27 22:27:51 on ttys000
tinghoudeMacBook:~ tinghou$ ls
Desktop DownloadsMovies Pictures VM Library cd
Documents LibraryMusicPublic Workspaces
tinghoudeMacBook:~ tinghou$ cd /usr/local/mysql/bin/
tinghoudeMacBook:bin tinghou$ ls
innochecksum mysqlaccess
msql2mysql mysqlaccess.conf
my_print_defaults mysqladmin
myisam_ftdump mysqlbinlog
myisamchk mysqlbug
myisamlog mysqlcheck
myisampack mysqld
mysql mysqld-debug
mysql_client_test mysqld_multi
mysql_client_test_embedded mysqld_safe
mysql_config mysqldump
mysql_config_editor mysqldumpslow
mysql_convert_table_format mysqlhotcopy
mysql_embedded mysqlimport
mysql_find_rows mysqlshow
mysql_fix_extensions mysqlslap
mysql_plugin mysqltest
mysql_secure_installation mysqltest_embedded
mysql_setpermission perror
mysql_tzinfo_to_sql replace
mysql_upgrade resolve_stack_dump
mysql_waitpid resolveip
mysql_zap
tinghoudeMacBook:bin tinghou$ cd
tinghoudeMacBook:~ tinghou$ mysql -u root -p
Enter password: tinghoudeMacBook
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 171
Server version: 5.6.12 MySQL Community Server (GPL)
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| test |
+--------------------+
4 rows in set (0.01 sec)
mysql> use test;
Database changed
mysql> exit;
Bye
tinghoudeMacBook:~ tinghou$
bogon:~ tinghou$ mysqladmin -u root password "123456"
bogon:~ tinghou$ mysql -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 61
Server version: 5.6.12 MySQL Community Server (GPL)
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
mysql> create database textdb1;
Query OK, 1 row affected (0.00 sec)
mysql> show create database textdb1;
+----------+--------------------------------------------------------------------+
| Database | Create Database |
+----------+--------------------------------------------------------------------+
| textdb1 | CREATE DATABASE `textdb1` /*!40100 DEFAULT CHARACTER SET latin1 */ |
+----------+--------------------------------------------------------------------+
1 row in set (0.00 sec)
mysql> use textdb1;
Database changed
mysql> select database();
+------------+
| database() |
+------------+
| textdb1 |
+------------+
1 row in set (0.00 sec)
mysql> select database();
+------------+
| database() |
+------------+
| textdb1 |
+------------+
1 row in set (0.00 sec)
mysql> create table t_user(
-> id int,
-> name varchar(20),
-> sal double(4,3),
-> birthday datetime,
-> hiredate timestamp
-> );
Query OK, 0 rows affected (0.03 sec)
mysql> show tables;
+-------------------+
| Tables_in_textdb1 |
+-------------------+
| t_user |
+-------------------+
1 row in set (0.00 sec)
mysql> desc t_user;
+----------+-------------+------+-----+-------------------+-----------------------------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+-------------------+-----------------------------+
| id | int(11) | YES | | NULL | |
| name | varchar(20) | YES | | NULL | |
| sal | double(4,3) | YES | | NULL | |
| birthday | datetime | YES | | NULL | |
| hiredate | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
+----------+-------------+------+-----+-------------------+-----------------------------+
5 rows in set (0.01 sec)
mysql>
2.测试：
mysql> create database day06;
Query OK, 1 row affected (0.00 sec)
mysql> use day06;
Database changed
mysql> create table users(
-> id int primary key auto_increment,
-> name varchar(40),
-> password varchar(40),
-> email varchar(60),
-> birthday date,
-> )character set utf8 collate utf8_general_ci;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')character set utf8 collate utf8_general_ci' at line 7
mysql> create table users(
-> id int primary key auto_increment,
-> name varchar(40),
-> password varchar(40),
-> email varchar(60),
-> birthday date
-> )character set utf8 collate utf8_general_ci;
Query OK, 0 rows affected (0.03 sec)
mysql> insert into users(name,password,email,birthday) values('zs','123456','zs@sina.com','1980-12-04');
Query OK, 1 row affected (0.00 sec)
mysql> insert into users(name,password,email,birthday) values('ls','123','ls@sina.com','1990-01-01');
Query OK, 1 row affected (0.01 sec)
mysql>
接着编写Java代码：
package com.me.jdbcdemo;import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;//使用JDBC技术实现查询数据库数据，并显示在控制台中
public class Demo1 {public static void main(String[] args) throws Exception {DriverManager.registerDriver(new com.mysql.jdbc.Driver());Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/day06", "root", "123456");Statement stmt = conn.createStatement();ResultSet rs = stmt.executeQuery("select password,email,birthday,id,name from users");while(rs.next()){ System.out.println(rs.getObject("password"));System.out.println(rs.getObject("id"));System.out.println(rs.getObject("name"));System.out.println(rs.getObject("birthday"));System.out.println(rs.getObject("email"));System.out.println("-----------------");}rs.close();stmt.close();conn.close();}}
运行：enjoy it！
二.常见的SQL语句
bogon:~ tinghou$ mysql -u root -p
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 98
Server version: 5.6.12 MySQL Community Server (GPL)
Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| day06 |
| mysql |
| performance_schema |
| test |
| testdb |
| textdb1 |
+--------------------+
7 rows in set (0.01 sec)
mysql> use day06;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> net stop mysql;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'net stop mysql' at line 1
mysql> show tables;
+-----------------+
| Tables_in_day06 |
+-----------------+
| users |
+-----------------+
1 row in set (0.00 sec)
mysql> desc users;
+----------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(40) | YES | | NULL | |
| password | varchar(40) | YES | | NULL | |
| email | varchar(60) | YES | | NULL | |
| birthday | date | YES | | NULL | |
+----------+-------------+------+-----+---------+----------------+
5 rows in set (0.02 sec)
mysql> select *from users;
+----+------+----------+-------------+------------+
| id | name | password | email | birthday |
+----+------+----------+-------------+------------+
| 1 | zs | 123456 | zs@sina.com | 1980-12-04 |
| 2 | ls | 123 | ls@sina.com | 1990-01-01 |
+----+------+----------+-------------+------------+
2 rows in set (0.00 sec)
mysql> select name from users;
+------+
| name |
+------+
| zs |
| ls |
+------+
2 rows in set (0.00 sec)
mysql> /*从新创建一个数据库*/
mysql> /*创建一个雇员表 体验常见的数据库操作*/
mysql> create table emp(
-> empno int,
-> ename varchar(50),
-> job varchar(50),
-> mgr int,
-> hiredate date,
-> sal decimal(7,2),
-> comm decimal(7,2),
-> deptno int
-> );
Query OK, 0 rows affected (0.05 sec)
mysql> show emp;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'emp' at line 1
mysql> desc emp;
+----------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+-------+
| empno | int(11) | YES | | NULL | |
| ename | varchar(50) | YES | | NULL | |
| job | varchar(50) | YES | | NULL | |
| mgr | int(11) | YES | | NULL | |
| hiredate | date | YES | | NULL | |
| sal | decimal(7,2) | YES | | NULL | |
| comm | decimal(7,2) | YES | | NULL | |
| deptno | int(11) | YES | | NULL | |
+----------+--------------+------+-----+---------+-------+
8 rows in set (0.01 sec)
mysql> /*查询所有列*/
mysql> select * from emp;
Empty set (0.00 sec)
mysql> INSERT INTO emp values(7369,'SMITH','CLERK',7902,'1980-12-17',800,NULL,20);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO emp values(7499,'ALLEN','SALESMAN',7698,'1981-02-20',1600,300,30);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO emp values(7521,'WARD','SALESMAN',7698,'1981-02-22',1250,500,30);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO emp values(7566,'JONES','MANAGER',7839,'1981-04-02',2975,NULL,20);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO emp values(7654,'MARTIN','SALESMAN',7698,'1981-09-28',1250,1400,30);
Query OK, 1 row affected (0.01 sec)
mysql> INSERT INTO emp values(7698,'BLAKE','MANAGER',7839,'1981-05-01',2850,NULL,30);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO emp values(7782,'CLARK','MANAGER',7839,'1981-06-09',2450,NULL,10);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO emp values(7788,'SCOTT','ANALYST',7566,'1987-04-19',3000,NULL,20);
Query OK, 1 row affected (0.01 sec)
mysql> INSERT INTO emp values(7839,'KING','PRESIDENT',NULL,'1981-11-17',5000,NULL,10);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO emp values(7844,'TURNER','SALESMAN',7698,'1981-09-08',1500,0,30);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO emp values(7876,'ADAMS','CLERK',7788,'1987-05-23',1100,NULL,20);
Query OK, 1 row affected (0.01 sec)
mysql> INSERT INTO emp values(7900,'JAMES','CLERK',7698,'1981-12-03',950,NULL,30);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO emp values(7902,'FORD','ANALYST',7566,'1981-12-03',3000,NULL,20);
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO emp values(7934,'MILLER','CLERK',7782,'1982-01-23',1300,NULL,10);
Query OK, 1 row affected (0.01 sec)
mysql> select * from emp;
+-------+--------+-----------+------+------------+---------+---------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------+--------+-----------+------+------------+---------+---------+--------+
| 7369 | SMITH | CLERK | 7902 | 1980-12-17 | 800.00 | NULL | 20 |
| 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 | 1600.00 | 300.00 | 30 |
| 7521 | WARD | SALESMAN | 7698 | 1981-02-22 | 1250.00 | 500.00 | 30 |
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 | 2975.00 | NULL | 20 |
| 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 | 1250.00 | 1400.00 | 30 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 | 2850.00 | NULL | 30 |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 | 2450.00 | NULL | 10 |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 | 3000.00 | NULL | 20 |
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 | 5000.00 | NULL | 10 |
| 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 | 1500.00 | 0.00 | 30 |
| 7876 | ADAMS | CLERK | 7788 | 1987-05-23 | 1100.00 | NULL | 20 |
| 7900 | JAMES | CLERK | 7698 | 1981-12-03 | 950.00 | NULL | 30 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 | 3000.00 | NULL | 20 |
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 | 1300.00 | NULL | 10 |
+-------+--------+-----------+------+------------+---------+---------+--------+
14 rows in set (0.00 sec)
mysql> /*查询指定列*/
mysql> select ename from emp;
+--------+
| ename |
+--------+
| SMITH |
| ALLEN |
| WARD |
| JONES |
| MARTIN |
| BLAKE |
| CLARK |
| SCOTT |
| KING |
| TURNER |
| ADAMS |
| JAMES |
| FORD |
| MILLER |
+--------+
14 rows in set (0.00 sec)
mysql> select ename,job from emp;
+--------+-----------+
| ename | job |
+--------+-----------+
| SMITH | CLERK |
| ALLEN | SALESMAN |
| WARD | SALESMAN |
| JONES | MANAGER |
| MARTIN | SALESMAN |
| BLAKE | MANAGER |
| CLARK | MANAGER |
| SCOTT | ANALYST |
| KING | PRESIDENT |
| TURNER | SALESMAN |
| ADAMS | CLERK |
| JAMES | CLERK |
| FORD | ANALYST |
| MILLER | CLERK |
+--------+-----------+
14 rows in set (0.00 sec)
mysql> /*创建一个学生表*/
mysql> create table stu(
-> sid char(6),
-> sname varchar(50),
-> age int,
-> gender varchar(50)
-> );
Query OK, 0 rows affected (0.03 sec)
mysql> INSERT INTO stu VALUES('S_1001', 'liuYi', 35, 'male');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO stu VALUES('S_1002', 'chenEr', 15, 'female');
Query OK, 1 row affected (0.01 sec)
mysql> INSERT INTO stu VALUES('S_1003', 'zhangSan', 95, 'male');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO stu VALUES('S_1004', 'liSi', 65, 'female');
Query OK, 1 row affected (0.01 sec)
mysql> INSERT INTO stu VALUES('S_1005', 'wangWu', 55, 'male');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO stu VALUES('S_1006', 'zhaoLiu', 75, 'female');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO stu VALUES('S_1007', 'sunQi', 25, 'male');
Query OK, 1 row affected (0.01 sec)
mysql> INSERT INTO stu VALUES('S_1008', 'zhouBa', 45, 'female');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO stu VALUES('S_1009', 'wuJiu', 85, 'male');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO stu VALUES('S_1010', 'zhengShi', 5, 'female');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO stu VALUES('S_1011', 'xxx', NULL, NULL);
Query OK, 1 row affected (0.00 sec)
mysql> desc stu;
+--------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+-------+
| sid | char(6) | YES | | NULL | |
| sname | varchar(50) | YES | | NULL | |
| age | int(11) | YES | | NULL | |
| gender | varchar(50) | YES | | NULL | |
+--------+-------------+------+-----+---------+-------+
4 rows in set (0.01 sec)
mysql> select *from stu;
+--------+----------+------+--------+
| sid | sname | age | gender |
+--------+----------+------+--------+
| S_1001 | liuYi | 35 | male |
| S_1002 | chenEr | 15 | female |
| S_1003 | zhangSan | 95 | male |
| S_1004 | liSi | 65 | female |
| S_1005 | wangWu | 55 | male |
| S_1006 | zhaoLiu | 75 | female |
| S_1007 | sunQi | 25 | male |
| S_1008 | zhouBa | 45 | female |
| S_1009 | wuJiu | 85 | male |
| S_1010 | zhengShi | 5 | female |
| S_1011 | xxx | NULL | NULL |
+--------+----------+------+--------+
11 rows in set (0.00 sec)
mysql> /*查询性别为女，并且年龄为50的记录*/
mysql> select * from stu where gender='female' and age<50;
+--------+----------+------+--------+
| sid | sname | age | gender |
+--------+----------+------+--------+
| S_1002 | chenEr | 15 | female |
| S_1008 | zhouBa | 45 | female |
| S_1010 | zhengShi | 5 | female |
+--------+----------+------+--------+
3 rows in set (0.00 sec)
mysql> /*查询学号为s_1001,s_1002)的记录*/
mysql> select * from stu where sid in('s_1001','s_1002');
+--------+--------+------+--------+
| sid | sname | age | gender |
+--------+--------+------+--------+
| S_1001 | liuYi | 35 | male |
| S_1002 | chenEr | 15 | female |
+--------+--------+------+--------+
2 rows in set (0.00 sec)
mysql> /*查询学号为s_1001，或者姓名为liuYi的记录*/
mysql> select * from stu where sid ='s_1001' or sname = 'liuYi';
+--------+-------+------+--------+
| sid | sname | age | gender |
+--------+-------+------+--------+
| S_1001 | liuYi | 35 | male |
+--------+-------+------+--------+
1 row in set (0.00 sec)
mysql> /*查询学号不是S_1001，S_1002，S_1003的记录*/
mysql> SELECT * FROM tab_student
-> WHERE s_number NOT IN ('S_1001','S_1002','S_1003');
ERROR 1146 (42S02): Table 'day06.tab_student' doesn't exist
mysql> SELECT * FROM tab_student WHERE s_number NOT IN ('S_1001','S_1002','S_1003');
ERROR 1146 (42S02): Table 'day06.tab_student' doesn't exist
mysql> SELECT * FROM stu WHERE s_number NOT IN ('S_1001','S_1002','S_1003');
ERROR 1054 (42S22): Unknown column 's_number' in 'where clause'
mysql> select * from stu where sid not in('S_1001','S_1002','S_1003');
+--------+----------+------+--------+
| sid | sname | age | gender |
+--------+----------+------+--------+
| S_1004 | liSi | 65 | female |
| S_1005 | wangWu | 55 | male |
| S_1006 | zhaoLiu | 75 | female |
| S_1007 | sunQi | 25 | male |
| S_1008 | zhouBa | 45 | female |
| S_1009 | wuJiu | 85 | male |
| S_1010 | zhengShi | 5 | female |
| S_1011 | xxx | NULL | NULL |
+--------+----------+------+--------+
8 rows in set (0.00 sec)
mysql> /*查询年龄为Null的记录*/
mysql> select *from stu where age is null;
+--------+-------+------+--------+
| sid | sname | age | gender |
+--------+-------+------+--------+
| S_1011 | xxx | NULL | NULL |
+--------+-------+------+--------+
1 row in set (0.00 sec)
mysql> /*查询年龄在20岁到40岁之间的学生*/
mysql> select *from stu where age>=20 and age<=40;
+--------+-------+------+--------+
| sid | sname | age | gender |
+--------+-------+------+--------+
| S_1001 | liuYi | 35 | male |
| S_1007 | sunQi | 25 | male |
+--------+-------+------+--------+
2 rows in set (0.00 sec)
mysql> select *from stu where age between 20 and 40;
+--------+-------+------+--------+
| sid | sname | age | gender |
+--------+-------+------+--------+
| S_1001 | liuYi | 35 | male |
| S_1007 | sunQi | 25 | male |
+--------+-------+------+--------+
2 rows in set (0.01 sec)
mysql> /*查询性别非男生的学生记录*/
mysql> select *from stu where gender<>'male';
+--------+----------+------+--------+
| sid | sname | age | gender |
+--------+----------+------+--------+
| S_1002 | chenEr | 15 | female |
| S_1004 | liSi | 65 | female |
| S_1006 | zhaoLiu | 75 | female |
| S_1008 | zhouBa | 45 | female |
| S_1010 | zhengShi | 5 | female |
+--------+----------+------+--------+
5 rows in set (0.00 sec)
mysql> select *from stu where not gender='male';
+--------+----------+------+--------+
| sid | sname | age | gender |
+--------+----------+------+--------+
| S_1002 | chenEr | 15 | female |
| S_1004 | liSi | 65 | female |
| S_1006 | zhaoLiu | 75 | female |
| S_1008 | zhouBa | 45 | female |
| S_1010 | zhengShi | 5 | female |
+--------+----------+------+--------+
5 rows in set (0.01 sec)
mysql> /*查询姓名不为null的记录*/
mysql> select *from stu where sname is not null;
+--------+----------+------+--------+
| sid | sname | age | gender |
+--------+----------+------+--------+
| S_1001 | liuYi | 35 | male |
| S_1002 | chenEr | 15 | female |
| S_1003 | zhangSan | 95 | male |
| S_1004 | liSi | 65 | female |
| S_1005 | wangWu | 55 | male |
| S_1006 | zhaoLiu | 75 | female |
| S_1007 | sunQi | 25 | male |
| S_1008 | zhouBa | 45 | female |
| S_1009 | wuJiu | 85 | male |
| S_1010 | zhengShi | 5 | female |
| S_1011 | xxx | NULL | NULL |
+--------+----------+------+--------+
11 rows in set (0.00 sec)
mysql> select *from stu where not sname is null;
+--------+----------+------+--------+
| sid | sname | age | gender |
+--------+----------+------+--------+
| S_1001 | liuYi | 35 | male |
| S_1002 | chenEr | 15 | female |
| S_1003 | zhangSan | 95 | male |
| S_1004 | liSi | 65 | female |
| S_1005 | wangWu | 55 | male |
| S_1006 | zhaoLiu | 75 | female |
| S_1007 | sunQi | 25 | male |
| S_1008 | zhouBa | 45 | female |
| S_1009 | wuJiu | 85 | male |
| S_1010 | zhengShi | 5 | female |
| S_1011 | xxx | NULL | NULL |
+--------+----------+------+--------+
11 rows in set (0.00 sec)
mysql> /*模糊查询：当想查询mysql> 模糊查询：当想查询姓名当中包含了字母a的时候 询mysql> 模糊查询：当想查询姓名当中包含了字母a的时候就需要使用模糊查询了。模糊查询需要使用关键字 like 通配符： _ 任意一个字符 %：任意0~n个字符 '%张%' '张_'*/
->
->
-> select *from stu;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '模糊查询：当想查询姓名当中包含了字母a的时候就需要使用' at line 1
mysql> /*查询由5个字母构成的学生记录*/
mysql> select * from stu where sname like '-----';
Empty set (0.00 sec)
mysql> select *from stu where sname like '---'
-> ;
Empty set (0.00 sec)
mysql> select *from stu where sname like '--';
Empty set (0.00 sec)
mysql> select * from stu where sname LIKE '------';
Empty set (0.00 sec)
mysql> /*查询姓名由5个字母构成，并且第5个字母为“i”的学生记录*/
mysql> select * from stu where sname like '----i';
Empty set (0.00 sec)
mysql> select from stu;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'from stu' at line 1
mysql> selcet *from stu;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'selcet *from stu' at line 1
mysql> select * from stu;
+--------+----------+------+--------+
| sid | sname | age | gender |
+--------+----------+------+--------+
| S_1001 | liuYi | 35 | male |
| S_1002 | chenEr | 15 | female |
| S_1003 | zhangSan | 95 | male |
| S_1004 | liSi | 65 | female |
| S_1005 | wangWu | 55 | male |
| S_1006 | zhaoLiu | 75 | female |
| S_1007 | sunQi | 25 | male |
| S_1008 | zhouBa | 45 | female |
| S_1009 | wuJiu | 85 | male |
| S_1010 | zhengShi | 5 | female |
| S_1011 | xxx | NULL | NULL |
+--------+----------+------+--------+
11 rows in set (0.00 sec)
mysql> /**去去除重复记录（两行或两行以上记录中系列的上的数据都相同），例如emp表 中sal字段就存在相同的记录。当只查询emp表的sal字段时，那么会出现重复记录，那么想 去除重复记录，需要使用DISTINCT：*/
mysql> select distinct sal from emp;
+---------+
| sal |
+---------+
| 800.00 |
| 1600.00 |
| 1250.00 |
| 2975.00 |
| 2850.00 |
| 2450.00 |
| 3000.00 |
| 5000.00 |
| 1500.00 |
| 1100.00 |
| 950.00 |
| 1300.00 |
+---------+
12 rows in set (0.01 sec)
mysql> select sal from emp;
+---------+
| sal |
+---------+
| 800.00 |
| 1600.00 |
| 1250.00 |
| 2975.00 |
| 1250.00 |
| 2850.00 |
| 2450.00 |
| 3000.00 |
| 5000.00 |
| 1500.00 |
| 1100.00 |
| 950.00 |
| 3000.00 |
| 1300.00 |
+---------+
14 rows in set (0.00 sec)
mysql> /*查看雇员的月薪与佣金之和*/
mysql> select *,sal+comm from emp;
+-------+--------+-----------+------+------------+---------+---------+--------+----------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno | sal+comm |
+-------+--------+-----------+------+------------+---------+---------+--------+----------+
| 7369 | SMITH | CLERK | 7902 | 1980-12-17 | 800.00 | NULL | 20 | NULL |
| 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 | 1600.00 | 300.00 | 30 | 1900.00 |
| 7521 | WARD | SALESMAN | 7698 | 1981-02-22 | 1250.00 | 500.00 | 30 | 1750.00 |
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 | 2975.00 | NULL | 20 | NULL |
| 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 | 1250.00 | 1400.00 | 30 | 2650.00 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 | 2850.00 | NULL | 30 | NULL |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 | 2450.00 | NULL | 10 | NULL |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 | 3000.00 | NULL | 20 | NULL |
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 | 5000.00 | NULL | 10 | NULL |
| 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 | 1500.00 | 0.00 | 30 | 1500.00 |
| 7876 | ADAMS | CLERK | 7788 | 1987-05-23 | 1100.00 | NULL | 20 | NULL |
| 7900 | JAMES | CLERK | 7698 | 1981-12-03 | 950.00 | NULL | 30 | NULL |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 | 3000.00 | NULL | 20 | NULL |
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 | 1300.00 | NULL | 10 | NULL |
+-------+--------+-----------+------+------------+---------+---------+--------+----------+
14 rows in set (0.00 sec)
mysql> /** comm列有很多记录的值为NULL，因为任何东西与NULL相加结果还是NULL，所以 结算结果可能会出现NULL。下面使用了把NULL转换成数值0的函数IFNULL：*/
mysql> select *,sal+ifnull(comm,0) from emp;
+-------+--------+-----------+------+------------+---------+---------+--------+--------------------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno | sal+ifnull(comm,0) |
+-------+--------+-----------+------+------------+---------+---------+--------+--------------------+
| 7369 | SMITH | CLERK | 7902 | 1980-12-17 | 800.00 | NULL | 20 | 800.00 |
| 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 | 1600.00 | 300.00 | 30 | 1900.00 |
| 7521 | WARD | SALESMAN | 7698 | 1981-02-22 | 1250.00 | 500.00 | 30 | 1750.00 |
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 | 2975.00 | NULL | 20 | 2975.00 |
| 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 | 1250.00 | 1400.00 | 30 | 2650.00 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 | 2850.00 | NULL | 30 | 2850.00 |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 | 2450.00 | NULL | 10 | 2450.00 |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 | 3000.00 | NULL | 20 | 3000.00 |
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 | 5000.00 | NULL | 10 | 5000.00 |
| 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 | 1500.00 | 0.00 | 30 | 1500.00 |
| 7876 | ADAMS | CLERK | 7788 | 1987-05-23 | 1100.00 | NULL | 20 | 1100.00 |
| 7900 | JAMES | CLERK | 7698 | 1981-12-03 | 950.00 | NULL | 30 | 950.00 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 | 3000.00 | NULL | 20 | 3000.00 |
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 | 1300.00 | NULL | 10 | 1300.00 |
+-------+--------+-----------+------+------------+---------+---------+--------+--------------------+
14 rows in set (0.00 sec)
mysql> /**给列名添加别名：在上面查询中出现列名为sal+IFNULL(comm,0)，这很不美观，现在我们给这一列给出一个别名，为total：*/
mysql> select *,sal+ifnull(comm,0) as total from emp;
+-------+--------+-----------+------+------------+---------+---------+--------+---------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno | total |
+-------+--------+-----------+------+------------+---------+---------+--------+---------+
| 7369 | SMITH | CLERK | 7902 | 1980-12-17 | 800.00 | NULL | 20 | 800.00 |
| 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 | 1600.00 | 300.00 | 30 | 1900.00 |
| 7521 | WARD | SALESMAN | 7698 | 1981-02-22 | 1250.00 | 500.00 | 30 | 1750.00 |
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 | 2975.00 | NULL | 20 | 2975.00 |
| 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 | 1250.00 | 1400.00 | 30 | 2650.00 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 | 2850.00 | NULL | 30 | 2850.00 |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 | 2450.00 | NULL | 10 | 2450.00 |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 | 3000.00 | NULL | 20 | 3000.00 |
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 | 5000.00 | NULL | 10 | 5000.00 |
| 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 | 1500.00 | 0.00 | 30 | 1500.00 |
| 7876 | ADAMS | CLERK | 7788 | 1987-05-23 | 1100.00 | NULL | 20 | 1100.00 |
| 7900 | JAMES | CLERK | 7698 | 1981-12-03 | 950.00 | NULL | 30 | 950.00 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 | 3000.00 | NULL | 20 | 3000.00 |
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 | 1300.00 | NULL | 10 | 1300.00 |
+-------+--------+-----------+------+------------+---------+---------+--------+---------+
14 rows in set (0.01 sec)
mysql> /**排序 order by 列名 asc(默认) desc*/
mysql> select * from stu order by age desc;
+--------+----------+------+--------+
| sid | sname | age | gender |
+--------+----------+------+--------+
| S_1003 | zhangSan | 95 | male |
| S_1009 | wuJiu | 85 | male |
| S_1006 | zhaoLiu | 75 | female |
| S_1004 | liSi | 65 | female |
| S_1005 | wangWu | 55 | male |
| S_1008 | zhouBa | 45 | female |
| S_1001 | liuYi | 35 | male |
| S_1007 | sunQi | 25 | male |
| S_1002 | chenEr | 15 | female |
| S_1010 | zhengShi | 5 | female |
| S_1011 | xxx | NULL | NULL |
+--------+----------+------+--------+
11 rows in set (0.01 sec)
mysql> /*查询所有雇员，按月薪降序排序，如果月薪相同时，按编号升序排序*/
mysql> select * from emp order by desc empno asc;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'desc empno asc' at line 1
mysql> select * from emp order by sal desc,empno asc;
+-------+--------+-----------+------+------------+---------+---------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------+--------+-----------+------+------------+---------+---------+--------+
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 | 5000.00 | NULL | 10 |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 | 3000.00 | NULL | 20 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 | 3000.00 | NULL | 20 |
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 | 2975.00 | NULL | 20 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 | 2850.00 | NULL | 30 |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 | 2450.00 | NULL | 10 |
| 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 | 1600.00 | 300.00 | 30 |
| 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 | 1500.00 | 0.00 | 30 |
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 | 1300.00 | NULL | 10 |
| 7521 | WARD | SALESMAN | 7698 | 1981-02-22 | 1250.00 | 500.00 | 30 |
| 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 | 1250.00 | 1400.00 | 30 |
| 7876 | ADAMS | CLERK | 7788 | 1987-05-23 | 1100.00 | NULL | 20 |
| 7900 | JAMES | CLERK | 7698 | 1981-12-03 | 950.00 | NULL | 30 |
| 7369 | SMITH | CLERK | 7902 | 1980-12-17 | 800.00 | NULL | 20 |
+-------+--------+-----------+------+------------+---------+---------+--------+
14 rows in set (0.00 sec)
mysql> /** 聚合函数 sum avg max min count*/
mysql> 聚合函数是用来做纵向运算的函数：
-> λCOUNT()：统计指定列不为NULL的记录行数；
-> λMAX()：计算指定列的最大值，如果指定列是字符串类型，那么使用字符串排序运 算；
-> λMIN()：计算指定列的最小值，如果指定列是字符串类型，那么使用字符串排序运 算；
-> λSUM()：计算指定列的数值和，如果指定列类型不是数值类型，那么计算结果为0；
-> λAVG()：计算指定列的平均值，如果指定列类型不是数值类型，那么计算结果为0；
-> */
-> select count(*) as cnt from emp;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '聚合函数是用来做纵向运算的函数：
λCOUNT()：统计指定列不' at line 1
mysql> select count(*) as cnt from emp;
+-----+
| cnt |
+-----+
| 14 |
+-----+
1 row in set (0.01 sec)
mysql> /*上面是查询emp表中记录数*/
mysql> /*查询emp表中有佣金的人数*/
mysql> select count(comm)cnt from emp;
+-----+
| cnt |
+-----+
| 4 |
+-----+
1 row in set (0.00 sec)
mysql> /*统计月薪与佣金纸盒大于2500元的人数*/
mysql> select count(*) as cnt from emp where sal+ifnull(comm,0)>2500;
+-----+
| cnt |
+-----+
| 6 |
+-----+
1 row in set (0.01 sec)
mysql> /*查询有佣金的人数,有领导的人数*/
mysql> select count(comm),count(mgr)from emp;
+-------------+------------+
| count(comm) | count(mgr) |
+-------------+------------+
| 4 | 13 |
+-------------+------------+
1 row in set (0.00 sec)
mysql> /*查询所有雇员月薪和，以及所有雇员佣金和*/
mysql> select sum(sal),sum(comm) from emp;
+----------+-----------+
| sum(sal) | sum(comm) |
+----------+-----------+
| 29025.00 | 2200.00 |
+----------+-----------+
1 row in set (0.00 sec)
mysql> /*查询所有雇员月薪+佣金和*/
mysql> SELECT SUM(sal+IFNULL(comm,0)) FROM emp;
+-------------------------+
| SUM(sal+IFNULL(comm,0)) |
+-------------------------+
| 31225.00 |
+-------------------------+
1 row in set (0.00 sec)
mysql> /*统计所有员工平均工资*/
mysql> SELECT AVG(sal) FROM emp;
+-------------+
| AVG(sal) |
+-------------+
| 2073.214286 |
+-------------+
1 row in set (0.00 sec)
mysql> /*λ查询最高工资和最低工资：
/*> select max(sal),min(sal)from emp;
/*> */
mysql> select max(sal),min(sal)from emp;
+----------+----------+
| max(sal) | min(sal) |
+----------+----------+
| 5000.00 | 800.00 |
+----------+----------+
1 row in set (0.00 sec)
mysql> /*查询每个部门的部门编号和每个部门的工资和*/
mysql> select deptno,sum(sal) from emp group by deptno;
+--------+----------+
| deptno | sum(sal) |
+--------+----------+
| 10 | 8750.00 |
| 20 | 10875.00 |
| 30 | 9400.00 |
+--------+----------+
3 rows in set (0.00 sec)
mysql> /*查询每个部门的部门编号以及每个部门的人数*/
mysql> select deptno,count(*) from emp group by deptno;
+--------+----------+
| deptno | count(*) |
+--------+----------+
| 10 | 3 |
| 20 | 5 |
| 30 | 6 |
+--------+----------+
3 rows in set (0.00 sec)
mysql> /*查询每个部门的部门编号以及每个部门工资大于1500的人数*/
mysql> select depno,count(*) from emp where sal>1500 group by deptno;
ERROR 1054 (42S22): Unknown column 'depno' in 'field list'
mysql> select deptno,count(*) from emp where sal>1500 group by deptno;
+--------+----------+
| deptno | count(*) |
+--------+----------+
| 10 | 2 |
| 20 | 3 |
| 30 | 2 |
+--------+----------+
3 rows in set (0.00 sec)
mysql>
一、SQL简介
Structured Query Language 结构化查询语言
作用：与数据库进行交互
知识扩展：
SQL标准，由ANSI（美国标准学会，属于ISO的核心成员）进行管理和维护的。
数据库厂商都支持该标准，并进行了扩展。扩展的部分，一般称之为方言。
SQL标准和方言：普通话和方言。
二、常用的数据库
1、Oracle
2、DB2
3、MySQL
4、SQL Server
三、安装MySQL
验证是否安装成功：
登录数据库：
shell>mysql -u root -p
四、数据库的基本概念：
知识点：使用关键字作为表名或数据库名或字段名，使用``（反引号）引起来
约定：shell>命令 windows命令
mysql>命令 mysql命令或语句
User类对应User表结构
User对象对应User表中的一条记录
五、SQL语句的分类：
*DDL：Data Definition Language数据定义语言
*DML：Data Manipulation Language 数据操作语言
DCL：Data Control Language 数据控制语言
*DQL：Data Query Language 数据查询语言
*TPL：事务处理语言
六、DDL：数据定义语言
作用：定义数据库或表结构用的
关键字：CREATE ALTER DROP
6.1数据库结构操作：
--------------------------------
创建一个名称为mydb1的数据库。
mysql>CREATE DATABASE mydb1; (字符集采用数据库默认的--安装时的那个)
查看数据库的创建细节
mysql>SHOW CREATE DATABASE mydb1;
查看当前所有的数据库
mysql>SHOW DATABASES;
创建一个使用gbk字符集的mydb2数据库。
mysql>CREATE DATABASE mydb2 CHARACTERSET gbk;
创建一个使用utf8字符集，并带校对规则的mydb3数据库。
mysql>CREATE DATABASE mydb3 CHARACTERSET utf8 COLLATE utf8_general_ci;
查看当前数据库服务器中的所有数据库
mysql>SHOW DATABASES;
查看前面创建的mydb2数据库的定义信息
mysql>SHOW CREATE DATABASE mydb2;
删除前面创建的mydb1数据库
mysql>DROP DATABASE mydb1;
查看服务器中的数据库，并把mydb2的字符集修改为utf8;
mysql>ALTER DATABASE mydb2 CHARACTER SETutf8;
--------------------------------
6.2表结构操作
创建表之前要先选择数据库。
选择数据库
mysql>USE mydb2;
创建一个员工表
mysql>CREATE TABLE employee(
idint,
namevarchar(100),
gendervarchar(10),
birthdaydate,
entry_datedate,
jobvarchar(100),
salaryfloat(8,2),
resumetext
);
查看当前数据库中的所有表
mysql>SHOW TABLES;
查看表的创建细节
mysql>SHOW CREATE TABLE employee;
在上面员工表的基本上增加一个image列。
mysql>ALTER TABLE employee ADD imageblob;
修改job列，使其长度为60。
mysql>ALTER TABLE employee MODIFYjob varchar(60);
删除image列。
mysql>ALTER TABLE employee DROP image;
表名改为user。
mysql>RENAME TABLE employee TO user;
修改表的字符集为utf8
mysql>ALTER TABLE user CHARACTER SETgbk;
列名name修改为username
mysql>ALTER TABLE user CHANGEname username varchar(100);
七、DML:数据操作语言
作用：操作的是表中的记录（数据）
关键字：INSERT UPDATE DELETE
MySQL:
字符串类型 使用单引号引起来 ‘abcdefg’
日期时间 使用单引号引起来 ‘2001-01-08’
特殊值 null
7.1插入数据
---------------------------------
向user表中插入三条员工信息
mysql>INSERT INTOuser (id,username,gender,birthday,entry_date,job,salary,resume)VALUES(1,'zhw','male','1990-08-09','2014-03-29','CTO',10000,'description');
mysql>INSERT INTO userVALUES(2,'hch','female','1989-08-09','2014-03-29','CEO',10000,'aaaaaa');
mysql>INSERT INTO user (id,username,gender,birthday,entry_date,job,salary,resume)VALUES(3,'皇甫张军','male','1990-08-09','2014-03-29','UFO',10000,'帅锅一枚');
告知服务器客户端使用的编码为gbk
mysql>set character_set_client=gbk;
告知服务器客户端查看结果集用的编码为gbk；
mysql>set character_set_results=gbk;
7.2更新数据
------------------------------------
将所有员工薪水修改为5000元。
mysql>UPDATE user SET salary=5000;
将姓名为’zhw’的员工薪水修改为3000元。
mysql>UPDATE user SET salary=3000 WHEREusername=’zhw’;
将姓名为’hch’的员工薪水修改为4000元,job改为ccc。
mysql>UPDATE user SET salary=4000,job=’ccc’WHERE username=’hch’;
将”皇甫张军”的薪水在原有基础上增加1000元。
mysql>UPDATE user SET salary=salary+1000where username=’皇甫张军’;
7.3删除数据
--------------------------------------
删除表中名称为’zhw’的记录。
msyql>DELETE FROM user WHERE username=’zhw’;
删除表中所有记录。
方式一：
mysql>DELETE FROM user;
方式二：(属于DDL语句)
mysql>TRUNCATE TABLE user; 把整张表格摧毁，然后重建的表结构。这比一行一行的删除行要快很多
八、DQL：数据查询语言
作用：查询
关键字：SELECT
8.1简单查询
-----------------------------
查询表中所有学生的信息。
mysql>SELECT * FROM student;
查询表中所有学生的姓名和对应的英语成绩。
mysql>SELECT name,english FROMstudent; (投影查询)
过滤表中重复数据。
msyql>SELECT DISTINCT english FROMstudent;
在所有学生数学分数上加10分特长分。
mysql>SELECT name,math+10 FROM student;
统计每个学生的总分。
mysql>SELECT name,chinese+english+mathFROM student;
使用别名表示学生分数。
mysql>SELECT name AS 姓名,chinese+english+math 总分 FROM student;
查询姓名为王五的学生成绩
msyql>SELECT * FROM student WHERE name='王五';
查询英语成绩大于90分的同学
mysql>SELECT * FROM student WHEREenglish>90;
查询总分大于200分的所有同学
mysql>SELECT * FROM student WHERE(chinese+english+math)>200;
查询英语分数在 80－90之间的同学。
mysql>SELECT * FROM student WHERE englishBETWEEN 80 AND 90;
查询数学分数为89,90,91的同学。
mysql>SELECT * FROM student WHERE mathIN (89,90,91);
查询所有姓李的学生成绩。
mysql>SELECT * FROM student WHERE nameLIKE ‘李%’;
查询数学分>80，语文分>80的同学。
mysql>SELECT * FROM student WHEREmath>80 AND chinese>80;
对数学成绩排序后输出。
mysql>SELECT name,math FROM studentORDER BY math;
对总分排序后输出，然后再按从高到低的顺序输出
mysql>SELECT name,chinese+english+mathFROM student ORDER BY chinese+english+math DESC;
对姓李的学生语文成绩排序输出(由高到低)
msyql>SELECT name,chinese FROM studentWHERE name LIKE ‘李%’ ORDER BY chineseDESC;
九、数据完整性
1、数据完整性是为了保证插入到数据中的数据是正确的，它防止了用户可能的输入错误
2、分为三类
l 实体完整性
l 域完整性
l 参照完整性
9.1实体完整性
规定表的一行（即每一条记录）在表中是唯一的实体。实体完整性通过表的主键来实现
主键的特点：不能为null，必须有值，且不能重复。
主键分类：
逻辑主键：不代表实际意义，只是区分不同记录用的。比如id
业务主键：代表者具体的实际意义。比如身份证号 用户名
CREATE TABLE t2(
idint PRIMARY KEY,#PRIMARY KEY 声明id是主键
namevarchar(100)
);
CREATE TABLE t4(
idint,
namevarchar(100),
PRIMARY KEY(id)
);
CREATE TABLE t3(
idint PRIMARY KEY auto_increment,#auto_increment 数据库自动增长
namevarchar(100)
);
9.2域完整性
指数据库表的列（即字段）必须符合某种特定的数据类型或约束。
非空约束：not null
唯一约束：unique
CREATE TABLE t6(
idint PRIMARY KEY auto_increment,
usernamevarchar(100) not null unique, 非空和唯一约束
gendervarchar(10) not null 非空约束
);
9.3参照完整性（多表）
表间的关系：
一对多（用的最多）
多对多（用的很多）
一对一（几乎不用）
9.3.1一对多：部门和员工的关系
CREATE TABLE department(
idint primary key,
namevarchar(100)
);
CREATE TABLE employee(
idint primary key,
namevarchar(100),
salaryfloat(8,2),
department_idint,
CONSTRAINTdepartment_id_fk FOREIGN KEY(department_id) REFERENCES department(id)
);
9.3.2多对多：老师和学员
CREATE TABLE teacher(
idint primary key,
namevarchar(100),
salaryfloat(8,2)
);
CREATE TABLE student(
idint primary key,
namevarchar(100),
gradevarchar(10)
);
CREATE TABLE teacher_student(
t_idint,
s_idint,
CONSTRAINTt_id_fk FOREIGN KEY(t_id) REFERENCES teacher(id),
CONSTRAINTs_id_fk FOREIGN KEY(s_id) REFERENCES student(id),
PRIMARYKEY(t_id,s_id)
);
9.3.3一对一（了解）
l 按照外键关联：
CREATE TABLE person(
idint primary key,
namevarchar(100)
);
CREATE TABLE idcard(
idint primary key,
numbervarchar(20),
person_idint unique,
CONSTRAINTperson_id_fk FOREIGN KEY(person_id) REFERENCES person(id)
);
l 按照主键关联：
CREATE TABLE person(
idint primary key,
namevarchar(100)
);
CREATE TABLE idcard(
idint primary key,
numbervarchar(20),
CONSTRAINTperson_id_fk FOREIGN KEY(id) REFERENCES person(id)
);
十、DQL：数据查询复杂的（多表）
10.1连接查询（面试几率很大）
基本语法形式：FROM 表1连接类型表2 [on连接条件][where 筛选条件]
约定：表1在连接类型的左边，称之为左表
表2在连接类型的右边，称之为右表
l 交叉连接：cross join
返回左表和右表的笛卡尔积（左表5条记录 ，右表6条记录 5*6=30条）
select * from customer,orders;
select * from customer cross join orders;
l 内连接：inner join
返回满足连接条件的所有记录。
隐式内连接：(不使用inner join关键字)
select c.*,o.* from customer c,orders o where c.id=o.customer_id;
显式内连接：(使用inner join关键字)
select * from customer c inner join orders o on c.id=o.customer_id;
l 外连接：outer join
左外连接:left outer join=left join
返回满足连接条件的所有记录，同时返回左表中剩余的其他记录
查询所有客户，有订单的把订单也显示出来
select * from customer c left outer join orders o onc.id=o.customer_id;
右外连接:right outer join=right join
返回满足连接条件的所有记录，同时返回右表中剩余的其他记录
查询所有订单，同时打印订单所属的客户
select * from customer c right outer join orders o onc.id=o.customer_id;
10.2子查询
子查询也叫嵌套查询，是指在select子句或者where子句中又嵌入select查询语句
查询“陈冠希”的所有订单信息
select id fromcustomer where name=’陈冠希’;
select * fromorders where customer_id=1;
子查询：
select * fromorders where customer_id=(select id from customer where name=’陈冠希’);
10.3联合查询
union关键字。
联合查询能够合并两条查询语句的查询结果，去掉其中的重复数据行，然后返回没有重复数据行的查询结果
SELECT * FROM orders WHERE price>200UNION SELECT * FROM orders WHERE customer_id=1;
10.4报表查询（使用数据库提供的函数）
统计一个班级共有多少学生？
msyql>SELECT COUNT(*) FROM student;
统计数学成绩大于90的学生有多少个？
mysql>SELECT COUNT(*) FROM student WHEREmath>90;
统计总分大于250的人数有多少？
mysql>SELECT COUNT(*) FROM student WHERE(chinese+english+math)>250;
统计一个班级数学总成绩？
mysql>SELECT SUM(math) FROM student;
统计一个班级语文、英语、数学各科的总成绩
mysql>SELECTSUM(chinese),SUM(english),SUM(math) FROM student;
统计一个班级语文、英语、数学的成绩总和
mysql>SELECT SUM(chinese+english+math)FROM student;
统计一个班级语文成绩平均分
mysql>SELECT SUM(chinese)/COUNT(*) FROMstudent;
求一个班级数学平均分？
mysql>SELECT AVG(math) FROM student;
求一个班级总分平均分
mysql>SELECT AVG(chinese+english+math)FROM student;
求班级语文最高分和数学最低分
mysql>SELECT MAX(chinese) FROM student;
mysql>SELECT MIN(math) FROM student;
对订单表中商品归类后，显示每一类商品的总价
mysql>SELECT product,SUM(price) FROMorders GROUP BY product;
查询购买了几类商品，并且每类总价大于100的商品
mysql>SELECT product,SUM(price) FROMorders GROUP BY product HAVING SUM(price)>100;
十一、MySQL数据库的备份与恢复
1、备份
2、恢复
前提：必须先创建数据库的名称
方式一：进入MySQL
方式二：不用进入MySQL
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