数据库

-- 建立数据库
CREATE DATABASE mydbtest;
-- 删除数据库
DROP DATABASE mydbtest;
-- 建立表格
CREATE TABLE t_product(
id INT PRIMARY KEY AUTO_INCREMENT,
pname VARCHAR(20),
price INT,
createAddress VARCHAR(20),
createDate DATE
);
-- 插入数据
INSERT INTO t_product(pname,price,createAddress,createDate)
VALUES('电视机',1500,'四川','2017-03-14');
-- 查询全部
SELECT*FROM t_product;
-- 查询列为pname
SELECT pname FROM t_product;
-- 查询id为1
SELECT*FROM t_product WHERE id=1;
-- 模糊查询pname带有机的内容
SELECT*FROM t_product WHERE pname LIKE '%机%';
-- 删除id为1的行
DELETE FROM t_product WHERE id=1;
-- 修改id为1的价格
UPDATE t_product SET price='2000' WHERE id=1;

以上是mysql数据库的一些基本操作代码，熟练使用这些代码可以筛选出数据库表格中自己想要得数据；

mysql中的聚合函数：COUNT(*)  COUNT(列名)   统计行数，前者包括空属性，后者只统计有内容的行数；

　　　　　　　　　　SUM(列名)  　　　　　　　 求和　

　　　　　　　　　　AVG(列名)　　　　　　　　求平均值

MAX最大值 MIN最小值

SQL的执行顺序： 1.FROM 2.WHERE 3.GROUP BY　4.SELECT  5.HAVING 6. ORDER BY

如果返回一个值，外查询可以使用 = > <

如果返回多个值，使用in 或者 not in;

MYSQL与Java的链接：

试着将一个用户（用户id，用户名，用户密码，用户住址）的数据库表格与java链接，完成对象数据和关系数据的转换

首先建立个用户类

package project.hw0511.bean;

import java.sql.Date;

public class adminBean {
    /**用户id*/
    private int id;
    /**用户名*/
    private String accord;
    /**用户密码*/
    private String password;
    /**生日*/
    private Date birthday;

    public adminBean() {
        super();
        // TODO Auto-generated constructor stub
    }

    public adminBean(String accord, String password, Date birthday) {
        super();
        this.accord = accord;
        this.password = password;
        this.birthday = birthday;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getAccord() {
        return accord;
    }

    public void setAccord(String accord) {
        this.accord = accord;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Override
    public String toString() {
        return "adminBean [id=" + id + ", accord=" + accord + ", password=" + password + ", birthday=" + birthday + "]
";
    }

}

第二步：建立一个对数据库表格操作的接口

package project.hw0511.Iadmin;

import java.sql.Date;
import java.util.List;

import project.hw0511.bean.adminBean;

public interface Iadmin {
    /**
     * 添加用户
     * @param accord      用户名
     * @param pwd        用户密码
     * @param birthday    生日
     */
    public void add(adminBean bean);
    /**
     * 按用户id删除
     * @param id 用户id
     */
    public void del(int id);
    /**
     * 按用户id修改
     * @param id     用户id
     * @return        用户密码
     */
    public void updata(int id,String pwd);
    /**
     * 按用户id查找
     * @param id    用户id
     */
    public adminBean findById(int id);
    /**
     * 查询所有用户
     */
    public List<adminBean> findAll();
    /**
     * 按用户名模糊查询
     * @param accord 用户名
     */
    public List<adminBean> findByAccord(String accord);
    /**
     * 按用户生日查询
     * @param birthday 生日
     */
    public List<adminBean> findByBirthday(Date startDate,Date endDate);
    
    public boolean login(String accord,String pwd);


}

最后：建立操作的实体类链接接口，完成对数据库具体操作

package project.hw0511.adminImpl;

import java.sql.Connection;
import java.sql.Date;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import project.hw0511.Iadmin.Iadmin;
import project.hw0511.bean.adminBean;

public class adminImpl implements Iadmin {

    public static void main(String[] args) {
        adminImpl dao = new adminImpl();
        // dao.add(new adminBean("莱昂纳德", "666666", Date.valueOf("1999-12-12")));
        // dao.del(1);
        // dao.updata(1, "900611");
        // adminBean a = dao.findById(1);
        // System.out.println(a);
        // List<adminBean> list=dao.findAll();
        // System.out.println(list);
        // List<adminBean> list=dao.findByAccord("吉");
        // System.out.println(list);
        // List<adminBean> list=dao.findByBirthday(Date.valueOf("1990-01-01"),
        // Date.valueOf("2007-12-31"));
        // System.out.println(list);
        boolean log = dao.login("波波维奇", "222222");
        System.out.println(log);
    }

    @Override
    public void add(adminBean bean) {
        Connection con = null;
        PreparedStatement ps = null;
        try {
            Class.forName("org.gjt.mm.mysql.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/admin?characterEncoding=utf-8", "root",
                    "zxiaoyuer");
            ps = con.prepareStatement("insert into t_user(u_accord,u_password,u_birthday)values(?,?,?)");
            ps.setString(1, bean.getAccord());
            ps.setString(2, bean.getPassword());
            ps.setDate(3, bean.getBirthday());
            ps.executeUpdate();
        } catch (Exception e) {

            e.printStackTrace();
        } finally {
            try {
                ps.close();
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

    }

    @Override
    public void del(int id) {
        Connection con = null;
        PreparedStatement ps = null;

        try {
            Class.forName("org.gjt.mm.mysql.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/admin?characterEncoding=utf-8", "root",
                    "zxiaoyuer");
            ps = con.prepareStatement("DELETE FROM t_user WHERE id=?");
            ps.setInt(1, id);
            ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                ps.close();
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

    }

    @Override
    public void updata(int id, String pwd) {
        Connection con = null;
        PreparedStatement ps = null;

        try {
            Class.forName("org.gjt.mm.mysql.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/admin?characterEncoding=utf-8", "root",
                    "zxiaoyuer");
            ps = con.prepareStatement("UPDATE t_user SET u_password=? WHERE id=?;");
            ps.setString(1, pwd);
            ps.setInt(2, id);
            ps.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                ps.close();
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

    }

    @Override
    public adminBean findById(int id) {
        adminBean bean = new adminBean();
        Connection con = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            Class.forName("org.gjt.mm.mysql.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/admin?characterEncoding=utf-8", "root",
                    "zxiaoyuer");
            ps = con.prepareStatement("SELECT*FROM t_user WHERE id=?");
            ps.setInt(1, id);
            rs = ps.executeQuery();
            if (rs.next()) {
                bean.setId(rs.getInt("id"));
                bean.setAccord(rs.getString("u_accord"));
                bean.setPassword(rs.getString("u_password"));
                bean.setBirthday(rs.getDate("u_birthday"));

            }
        } catch (Exception e) {

            e.printStackTrace();
        } finally {
            try {
                rs.close();
                ps.close();
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }

        }
        return bean;

    }

    @Override
    public List<adminBean> findAll() {
        List<adminBean> list = new ArrayList<>();
        Connection con = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            Class.forName("org.gjt.mm.mysql.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/admin?characterEncoding=utf-8", "root",
                    "zxiaoyuer");
            ps = con.prepareStatement("SELECT*FROM t_user");
            rs = ps.executeQuery();

            while (rs.next()) {
                adminBean bean = new adminBean();
                bean.setId(rs.getInt("id"));
                bean.setAccord(rs.getString("u_accord"));
                bean.setPassword(rs.getString("u_password"));
                bean.setBirthday(rs.getDate("u_birthday"));
                list.add(bean);
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                rs.close();
                ps.close();
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        return list;

    }

    @Override
    public List<adminBean> findByAccord(String accord) {
        List<adminBean> list = new ArrayList<>();
        Connection con = null;
        PreparedStatement ps = null;
        ResultSet rs = null;

        try {
            Class.forName("org.gjt.mm.mysql.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/admin?characterEncoding=utf-8", "root",
                    "zxiaoyuer");
            ps = con.prepareStatement("SELECT*FROM t_user WHERE u_accord LIKE ?");
            ps.setString(1, "%" + accord + "%");
            rs = ps.executeQuery();
            while (rs.next()) {
                adminBean bean = new adminBean();
                bean.setId(rs.getInt("id"));
                bean.setAccord(rs.getString("u_accord"));
                bean.setPassword(rs.getString("u_password"));
                bean.setBirthday(rs.getDate("u_birthday"));
                list.add(bean);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                rs.close();
                ps.close();
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return list;

    }

    @Override
    public List<adminBean> findByBirthday(Date startDate, Date endDate) {
        List<adminBean> list = new ArrayList<>();
        Connection con = null;
        PreparedStatement ps = null;
        ResultSet rs = null;

        try {
            Class.forName("org.gjt.mm.mysql.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/admin?characterEncoding=utf-8", "root",
                    "zxiaoyuer");
            ps = con.prepareStatement("SELECT*FROM t_user WHERE u_birthday>=? AND u_birthday<=?");
            ps.setDate(1, startDate);
            ps.setDate(2, endDate);
            rs = ps.executeQuery();
            while (rs.next()) {
                adminBean bean = new adminBean();
                bean.setId(rs.getInt("id"));
                bean.setAccord(rs.getString("u_accord"));
                bean.setPassword(rs.getString("u_password"));
                bean.setBirthday(rs.getDate("u_birthday"));
                list.add(bean);
            }

        } catch (Exception e) {
        
            e.printStackTrace();
        } finally {
            try {
                rs.close();
                ps.close();
                con.close();
            } catch (SQLException e) {
                
                e.printStackTrace();
            }
        }
        return list;

    }

    @Override
    public boolean login(String accord, String pwd) {
        Connection con = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        try {
            Class.forName("org.gjt.mm.mysql.Driver");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/admin?characterEncoding=utf-8", "root",
                    "zxiaoyuer");
            ps = con.prepareStatement("SELECT u_password FROM t_user WHERE u_accord=?");
            ps.setString(1, accord);
            rs = ps.executeQuery();
            if (rs.next()) {
                if (rs.getString("u_password").equals(pwd)) {
                    return true;
                }
            }
        } catch (Exception e) {

            e.printStackTrace();
        } finally {
            try {
                rs.close();
                ps.close();
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        return false;
    }

}

需要注意的是：　　

con = DriverManager.getConnection("jdbc:mysql://localhost:3306/admin?characterEncoding=utf-8", "root",
                    "zxiaoyuer");
链接建立是，地址是否正确
            ps = con.prepareStatement("SELECT u_password FROM t_user WHERE u_accord=?");

　ps中的语句可以看成要在数据库中执行语句，建议在数据库中验证语句可用性，直接复制即可

ResultSet：结果集，只有在需要java接受或者显示实，需要结果集接受，和传递