java sql数据库

数据库连接

1、JDBC连接数据库

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
public class JdbcDemo {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/test";
        String username = "root";
        String password = "123456";
        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection connection = DriverManager.getConnection(url, username, password);
            System.out.println("数据库连接成功");
            connection.close();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

创建表

1、创建学生表

CREATE TABLE student (
    id INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(20) NOT NULL,
    age INT,
    gender ENUM('男', '女') NOT NULL,
    class_name VARCHAR(20) NOT NULL
);

插入数据

1、插入学生数据

INSERT INTO student (name, age, gender, class_name) VALUES ('张三', 18, '男', '计算机一班');
INSERT INTO student (name, age, gender, class_name) VALUES ('李四', 19, '女', '计算机一班');
INSERT INTO student (name, age, gender, class_name) VALUES ('王五', 20, '男', '计算机二班');

查询数据

1、查询所有学生信息

SELECT * FROM student;

2、查询某个班级的学生信息

SELECT * FROM student WHERE class_name = '计算机一班';

3、查询年龄大于等于18岁的学生信息

SELECT * FROM student WHERE age >= 18;

更新数据

1、更新学生年龄和班级信息

UPDATE student SET age = 21, class_name = '计算机三班' WHERE id = 1;

删除数据

1、删除某个学生信息

DELETE FROM student WHERE id = 2;