Mysql初次接触

hyytaojunming

//创建数据库
create database mydata;
//在mydata下面工作
use mydata;
//创建一张表dept
create table dept
(
deptno int primary key,
dname varchar(14),
loc varchar(13)
);
//创建一张表emp
create table emp
(
empno int primary key,
ename varchar(10),
job varchar(10),
mgr int,
hiredate datetime,
sal double,
comm double,
deptno int,
foreign key (deptno) references dept(deptno)
);
//执行一个sql文件中的语句
.\ d:\\mysql\\mydata.sql
//查看有几个数据库
show databases;
//查看当前数据库中有几张表
show tables;
//查看表dept的结构
desc dept;
//数据库分页(根据字段deptno倒序排列后，从第3条开始【不包括第3条】往后读取2条数据)
select * from dept order by deptno desc limit 3, 2;
注：limit后面不能跟括号，第一个参数最小从0开始，不能是负数；第二个参数没有限制，可以超出表中的记录数，比如：select * from dept order by deptno desc limit 0, 200;查出的就是表dept的所有数据
//自动递增字段(auto_increment)
create table article
(
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');
//获取系统当前时间(from dual可以不要)
select now() from dual;
2013-07-14 17:00:20
//日期格式转换
select date_format(now(), '%y-%m-%d %h:%i:%s');
13-07-14 05:00:31
select date_format(now(), '%Y-%M-%D %H:%I:%S');
2013-July-14th 17:00:31
//往datetime格式里面插入数据，字符只要格式一样的话，也可以插入
insert into emp values (10,'zhangsan','job1',20,'2013-4-5 12:45:14',8000,1231,30);
//JDBC链接mysql

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class TestJDBC {
public static void main(String[] args) {
ResultSet rs = null;
Statement stmt = null;
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
// Class.forName("com.mysql.jdbc.Driver").newInstance();
// new com.mysql.jdbc.Driver();
conn = DriverManager
.getConnection("jdbc:mysql://localhost:3306/mydata", "root", "root");
stmt = conn.createStatement();
rs = stmt.executeQuery("select * from dept");
while (rs.next()) {
System.out.println(rs.getString("dname") + "" + rs.getInt("deptno"));
}
} 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();
}
}
}
}

　　
//mysql树形展示
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
 );
--0表示leaf,1表示非leaf

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', '大象被打趴下', 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,'可能性很大的', '可能性很大的', 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,'蚂蚁是护士', '蚂蚁是护士', now(),0);

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
public class TestArticleTree {
public static void tree(Connection conn, int id, int level) {
Statement stmt = null;
ResultSet rs = null;
StringBuffer sb = new StringBuffer();
for (int i = 0; i < level; i++) {
sb.append("*****");
}
try {
stmt = conn.createStatement();
rs = stmt.executeQuery("select * from article where pid = " + id);
while (rs.next()) {
System.out.println(sb.toString() + rs.getString("cont"));
if (rs.getInt("isleaf") == 1) {
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();
}
}
}
public static void main(String[] args) {
ResultSet rs = null;
Statement stmt = null;
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/bbs", "root", "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();
}
}
}
}

 

结果：
蚂蚁大战大象
*****大象被打趴下
**********蚂蚁也不好过
**********瞎说
***************没有瞎说
**********大象进医院了
***************蚂蚁是护士
*****怎么可能
**********怎么没有可能
**********可能性很大的