JDBC练习-insert语句、update语句、DDL语句、select语句

JDBC练习-insert语句

public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            //1.注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2.定义sql
            String sql = "insert into account values(null,'老六',250)";
            //3.获取Connection对象
            conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "root");
            //4.获取执行sql的对象
            stmt = conn.createStatement();
            //5.执行sql
            int i = stmt.executeUpdate(sql);
            //6.处理结果
            System.out.println(i);
            if(i>0){
                System.out.println("添加成功");
            }else {
                System.out.println("添加失败");
            }
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }catch (SQLException e){
            e.printStackTrace();
        }finally {
            //7. 释放资源
//            stmt.close(); // 避免空指针异常
            if(stmt!=null){
                try {
                    stmt.close();
                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }
            }
           if (conn!=null){
               try {
                   conn.close();
               } catch (SQLException e) {
                   throw new RuntimeException(e);
               }
           }
        }
    }

 

JDBC练习-update语句

 public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            //1. 注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2. 获取连接对象
            conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "root");
            //3. 定义sql
            String sql = "update account set balance = 3000 where id = 4";
            //4. 获取执行sql对象
            stmt = conn.createStatement();
            //5. 执行sql
            int count = stmt.executeUpdate(sql);
            //6. 处理结果
            System.out.println(count);
            if(count>0){
                System.out.println("修改成功");
            }else {
                System.out.println("修改失败");
            }
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }finally {
            //7. 关流
            if(conn!=null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }
            }
            if(stmt!=null){
                try {
                    stmt.close();
                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }
            }
        }
    }

 

JDBC练习-DDL语句

public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            //1. 注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2. 获取连接对象
            conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "root");
            //3. 定义sql
            String sql = "delete  from account where id = 4";
            //4. 获取执行sql对象
            stmt = conn.createStatement();
            //5. 执行sql
            int count = stmt.executeUpdate(sql);
            //6. 处理结果
            System.out.println(count);
            if(count>0){
                System.out.println("删除成功");
            }else {
                System.out.println("删除失败");
            }
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }finally {
            //7. 关流
            if(conn!=null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }
            }
            if(stmt!=null){
                try {
                    stmt.close();
                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }
            }
        }
    }

 

public static void main(String[] args) {
        Connection conn = null;
        Statement stmt = null;
        try {
            //1. 注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2. 获取连接对象
            conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "root");
            //3. 定义sql
            String sql = "create table st (id int,name varchar(20))";
            //4. 获取执行sql对象
            stmt = conn.createStatement();
            //5. 执行sql
            int count = stmt.executeUpdate(sql);
            //6. 处理结果
            System.out.println(count);
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }finally {
            //7. 关流
            if(conn!=null){
                try {
                    conn.close();
                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }
            }
            if(stmt!=null){
                try {
                    stmt.close();
                } catch (SQLException e) {
                    throw new RuntimeException(e);
                }
            }
        }
    }

 

JDBC练习-select语句

Emp表需要和数据库里面的表的数据保持一致

 

 

 

public class Emp {
    private int id;
    private String ename;
    private int job_id;
    private int mgr;
    private Date joindate;
    private double salary;
    private double bonus;
    private int dept_id;

    public int getId() {
        return id;
    }

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

    public String getEname() {
        return ename;
    }

    public void setEname(String ename) {
        this.ename = ename;
    }

    public int getJob_id() {
        return job_id;
    }

    public void setJob_id(int job_id) {
        this.job_id = job_id;
    }

    public int getMgr() {
        return mgr;
    }

    public void setMgr(int mgr) {
        this.mgr = mgr;
    }

    public Date getJoindate() {
        return joindate;
    }

    public void setJoindate(Date joindate) {
        this.joindate = joindate;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public double getBonus() {
        return bonus;
    }

    public void setBonus(double bonus) {
        this.bonus = bonus;
    }

    public int getDept_id() {
        return dept_id;
    }

    public void setDept_id(int dept_id) {
        this.dept_id = dept_id;
    }

    @Override
    public String toString() {
        return "Emp{" +
                "id=" + id +
                ", ename='" + ename + '\'' +
                ", job_id=" + job_id +
                ", mgr=" + mgr +
                ", joindate=" + joindate +
                ", salary=" + salary +
                ", bonus=" + bonus +
                ", dept_id=" + dept_id +
                '}';
    }
}

 

JDBCDemo8类

public class JDBCDemo8 {
    /*
    定义一个方法，查询emp表的数据将其封装为对象，然后装载集合，返回
     */

    public static void main(String[] args) {
        List<Emp> all = new JDBCDemo8().findAll();
        for (Emp emp : all) {
            System.out.println(emp);
        }

    }

    public List<Emp> findAll() {
        ResultSet rs = null;
        Connection conn = null;
        Statement stat = null;
        List<Emp> list = null;
        try {
            //1. 注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            // 2.获取连接
            conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "root");
            // 3.定义数据库
            String sql = "select * from emp";
            // 4.获取执行sql的对象
            stat = conn.createStatement();
            // 5.执行sql
            rs = stat.executeQuery(sql);
            // 6.遍历结果集，封装对象，装载集合
            Emp emp = null;
            list = new ArrayList<Emp>();
            while (rs.next()) {
                int id = rs.getInt("id");
                String ename = rs.getString("ename");
                int job_id = rs.getInt("job_id");
                int mgr = rs.getInt("mgr");
                Date joindate = rs.getDate("joindate");
                double salary = rs.getDouble("salary");
                double bonus = rs.getDouble("bonus");
                int dept_id = rs.getInt("dept_id");

                emp = new Emp();
                emp.setId(id);
                emp.setEname(ename);
                emp.setJob_id(job_id);
                emp.setMgr(mgr);
                emp.setJoindate(joindate);
                emp.setSalary(salary);
                emp.setBonus(bonus);
                emp.setDept_id(dept_id);

                // 装载集合
                list.add(emp);

            }
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        } finally {
            if (conn != null) {
                try {
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (stat != null) {
                try {
                    stat.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if (rs != null) {
                try {
                    rs.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
        return list;
    }
}

 

运行结果