MySQL学习笔记
一、MySQL基本命令集合：
1、 create database mydata；//创建数据库
2、 use mydata; //在mydata这个数据库下工作
3、 create table dept //在mydata数据库下创建表dept
(
deptno int primary key,
dname varchar(14),
loc varchar(13)
);
create table emp //在mydata数据库下创建表emp
(
empno int primary key,
ename varchar(10),
job varchar(10),
mar int,
hiredate datetime,
sal double,
comm double,
deptno int,
foreign key (deptno) references dept(deptno)
);
4、 show databases；//显示数据库
5、 show tables；//显示表
6、 desc dept；//显示dept表的结构
7、 insert into dept values（10, ‘A’, ‘A’）；//向dept表中添加记录
insert into dept values（20, ‘B’, ‘B’）；
insert into dept values（30, ‘C’, ‘C’）；
commit； //提交
8、 select * from dept；//查询记录
select * from dept order by deptno desc limit 3,2；//显示记录
二、MySQL的自动递增：
create table article //创建自动递增表
(
Id int primary key auto_increment,
Title varchar(255)
);
Insert into article values(null,’a’);
Insert into article values(null,’b’);
Insert into article(title) values(‘c’);
三、MySQL的日期时间：
1、 select now（）；//显示当前时间
2、 select date_format(now( ),’%y-%m-%d %H：%i：%s’)；//显示指定格式的时间
四、MySQL_jdbc连接：
import java.sql.*;
public class TestMysqlConnection {
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager
.getConnection("jdbc:mysql://localhost/mydata?user=root&password=root");
stmt = conn.createStatement();
rs = stmt.executeQuery("select * from dept");
while (rs.next()) {
System.out.println(rs.getString("deptno"));
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException ex) {
System.out.println("SQLException: " + ex.getMessage());
System.out.println("SQLState: " + ex.getSQLState());
System.out.println("VendorError: " + ex.getErrorCode());
} finally {
try {
if (rs != null) {
rs.close();
rs = null;
}
if (stmt != null) {
stmt.close();
stmt = null;
}
if (conn != null) {
conn.close();
conn = null;
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
五、在MySQL中创建数据库和表：
在mysql中执行语句：\·E:\JDBC_MySQL_BBS项目\source\BBS\SQL\bbs.sql 可以执行bbs.sql中的语句
create database bbs;
use bbs;
create table article
(
id int primary key auto_increment,
pid int,
rootid int,
title varchar(255),
cont text,
pdate datetime,
isleaf int
);
insert into article values (null, 0, 1, '蚂蚁大战大象', '蚂蚁大战大象', now(), 1);
insert into article values (null, 1, 1, '大象被打趴下了', '大象被打趴下了',now(), 1);
insert into article values (null, 2, 1, '蚂蚁也不好过','蚂蚁也不好过', now(), 0);
insert into article values (null, 2, 1, '瞎说', '瞎说', now(), 1);
insert into article values (null, 4, 1, '没有瞎说', '没有瞎说', now(), 0);
insert into article values (null, 1, 1, '怎么可能', '怎么可能', now(), 1);
insert into article values (null, 6, 1, '怎么没有可能', '怎么没有可能', now(), 0);
insert into article values (null, 6, 1, '可能性是很大的', '可能性是很大的', now(), 0);
insert into article values (null, 2, 1, '大象进医院了', '大象进医院了', now(), 1);
insert into article values (null, 9, 1, '护士是蚂蚁', '护士是蚂蚁', now(), 0);
六、JDBC树状显示（tree）
import java.sql.*;
public class ArticleTree {
public static void main(String[] args) {
new ArticleTree().show();
}
public void show() {
Connection conn = null;
Statement stmt = null;
ResultSet rs = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager
.getConnection("jdbc:mysql://localhost/bbs?user=root&password=root");
stmt = conn.createStatement();
rs = stmt.executeQuery("select * from article where pid = 0");
while (rs.next()) {
System.out.println(rs.getString("cont"));
tree(conn, rs.getInt("id"), 1);
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (rs != null) {
rs.close();
rs = null;
}
if (stmt != null) {
stmt.close();
stmt = null;
}
if (conn != null) {
conn.close();
conn = null;
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
private void tree(Connection conn, int id, int level) {
Statement stmt = null;
ResultSet rs = null;
StringBuffer strPre = new StringBuffer("");
for (int i = 0; i < level; i++) {
strPre.append(" ");
}
try {
stmt = conn.createStatement();
String sql = "select * from article where pid = " + id;
rs = stmt.executeQuery(sql);
while (rs.next()) {
System.out.println(strPre + rs.getString("cont"));
if (rs.getInt("isleaf") != 0) {
tree(conn, rs.getInt("id"), level + 1);
}
}
} catch (SQLException e) {
e.printStackTrace();
} finally {
try {
if (rs != null) {
rs.close();
rs = null;
}
if (stmt != null) {
stmt.close();
stmt = null;
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}