[중앙정보기술인재개발원] 28일차

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이 과제의 목적은 인스타그램과 유사한 간단한 소셜 미디어 데이터베이스를 설계하고, JDBC를 사용하여 데이터베이스 관리 작업을 수행하는 것입니다.

과제 요구 사항

1. 데이터베이스 생성
   • 데이터베이스 이름은 instagram으로 설정합니다.
   • JDBC를 사용하여 데이터베이스를 생성하는 코드를 작성합니다.
2. 테이블 설계 및 생성

• 각 테이블의 스키마를 설계하고, 생성 쿼리를 작성합니다.

1. 데이터 삽입
   • JDBC를 사용하여 데이터 삽입 쿼리를 실행하는 코드를 작성합니다.
   • 삽입 데이터는 아래 내용을 참고합니다.

    String sqlInsertUsers = "INSERT INTO users (username, password) VALUES " +
                            "('user1', 'password1'), ('user2', 'password2'), ('user3', 'password3'), " +
                            "('user4', 'password4'), ('user5', 'password5'), ('user6', 'password6'), " +
                            "('user7', 'password7'), ('user8', 'password8'), ('user9', 'password9'), " +
                            "('user10', 'password10')";

    String sqlInsertPosts = "INSERT INTO posts (image, message, user_id) VALUES " +
                            "(NULL, 'Hello World', 1), (NULL, 'Learning Java', 2), " +
                            "(NULL, 'At the beach', 3), (NULL, 'Eating pizza', 4), " +
                            "(NULL, 'Watching a movie', 5), (NULL, 'At a concert', 6), " +
                            "(NULL, 'Playing games', 7), (NULL, 'Reading a book', 8), " +
                            "(NULL, 'Visiting museums', 9), (NULL, 'Going hiking', 10)";
		String sqlInsertComments = "INSERT INTO post_comments (comment, user_id, post_id) VALUES " +
                               "('Nice post!', 1, 1), ('Love this!', 2, 1), ('So cool!', 3, 2), " +
                               "('Wow!', 4, 3), ('Great pic!', 5, 3), ('Cant agree more!', 6, 4), " +
                               "('LOL', 7, 5), ('Thats awesome!', 8, 6), ('Yummy!', 9, 7), ('Interesting!', 10, 8)";
                               
    String sqlInsertLikes = "INSERT INTO post_likes (user_id, post_id) VALUES " +
                            "(1, 1), (2, 1), (3, 1), (4, 2), (5, 2), " +
                            "(6, 3), (7, 3), (8, 4), (9, 5), (10, 5)";

    String sqlInsertFollows = "INSERT INTO follow_follower (follower_id, user_id) VALUES " +
                              "(1, 2), (1, 3), (2, 3), (2, 4), (3, 4), " +
                              "(3, 5), (4, 5), (4, 6), (5, 6), (5, 7)";
    String sqlInsertHashtags = "INSERT INTO hashtags (name) VALUES " +
                               "('summer'), ('java'), ('beach'), ('pizza'), ('movie'), " +
                               "('concert'), ('games'), ('book'), ('museum'), ('hiking')";
    String sqlInsertPostsHashtags = "INSERT INTO posts_hashtags (hashtag_id, post_id) VALUES " +
                                    "(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), " +
                                    "(6, 6), (7, 7), (8, 8), (9, 9), (10, 10)";

 

- 데이터베이스 생성

package instagramref;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class CreatDatabase {
    public static void main(String[] args) {
        try {
            String URL = "jdbc:mysql://127.0.0.1:3306";
            String USER = "root";
            String PASSWORD = "11";

            Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
            Statement statement = conn.createStatement();

            String createDatabaseSQL = "" +
                    "CREATE DATABASE IF NOT EXISTS instagram";
            statement.execute(createDatabaseSQL);
            System.out.println("instagram 데이터베이스가 생성되었습니다.");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

 

- 테이블 생성

package instagramref;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class CreatTables {
    public static void main(String[] args) {
        try {
            String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
            String USER = "root";
            String PASSWORD = "11";

            Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
            Statement statement = conn.createStatement();

            String usersSQL = "CREATE TABLE Users ( " +
                    "id INT AUTO_INCREMENT PRIMARY KEY, " +
                    "username VARCHAR(255) NOT NULL, " +
                    "password VARCHAR(255) NOT NULL)";
            statement.execute(usersSQL);

            String follow_followerSQL = "CREATE TABLE follow_follower ( " +
                    "id INT AUTO_INCREMENT PRIMARY KEY, " +
                    "follower_id INT, " +
                    "user_id INT, " +
                    "FOREIGN KEY (follower_id) REFERENCES Users(id) ON DELETE CASCADE, " +
                    "FOREIGN KEY (user_id) REFERENCES Users(id) ON DELETE CASCADE)";

            statement.execute(follow_followerSQL);
            String postsSQL = "CREATE TABLE Posts ( " +
                    "id INT AUTO_INCREMENT PRIMARY KEY, " +
                    "image BLOB, " +
                    "message TEXT, " +
                    "created_at DATETIME DEFAULT CURRENT_TIMESTAMP, " +
                    "total_likes INT, " +
                    "total_comments INT, " +
                    "user_id INT, " +
                    "FOREIGN KEY (user_id) REFERENCES Users(id) ON DELETE CASCADE)";

            statement.execute(postsSQL);
            String hashtagSQL = "CREATE TABLE hashtags ( " +
                    "id INT AUTO_INCREMENT PRIMARY KEY, " +
                    "name VARCHAR(255))";

            statement.execute(hashtagSQL);
            String posthashtagSQL = "CREATE TABLE posts_hashtags ( " +
                    "id INT AUTO_INCREMENT PRIMARY KEY, " +
                    "hashtag_id INT, " +
                    "post_id INT, " +
                    "FOREIGN KEY (hashtag_id) REFERENCES hashtags(id) ON DELETE CASCADE, " +
                    "FOREIGN KEY (post_id) REFERENCES posts(id) ON DELETE CASCADE)";

            statement.execute(posthashtagSQL);
            String postlikeSQL = "CREATE TABLE post_likes ( " +
                    "id INT AUTO_INCREMENT PRIMARY KEY, " +
                    "created_at DATETIME DEFAULT CURRENT_TIMESTAMP, " +
                    "user_id INT, " +
                    "post_id INT, " +
                    "FOREIGN KEY (user_id) REFERENCES Users(id) ON DELETE CASCADE, " +
                    "FOREIGN KEY (post_id) REFERENCES Posts(id) ON DELETE CASCADE)";

            statement.execute(postlikeSQL);
            String postcommentSQL = "CREATE TABLE post_comments ( " +
                    "id INT AUTO_INCREMENT PRIMARY KEY, " +
                    "comment VARCHAR(255), " +
                    "created_at DATETIME DEFAULT CURRENT_TIMESTAMP, " +
                    "user_id INT, " +
                    "post_id INT, " +
                    "FOREIGN KEY (user_id) REFERENCES Users(id) ON DELETE CASCADE, " +
                    "FOREIGN KEY (post_id) REFERENCES Posts(id) ON DELETE CASCADE)";
            statement.execute(postcommentSQL);
//            System.out.println("instagram 데이터베이스가 생성되었습니다.");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

 

- 더미 데이터 추가

package instagramref;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class InsetIntoDummyData {
    public static void main(String[] args) {
        try {
            String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
            String user = "root";
            String password = "11";

            Connection conn = DriverManager.getConnection(URL, user, password);
            Statement stmt = conn.createStatement();

            String sqlInsertUsers = "INSERT INTO users (username, password) VALUES " +
                    "('user1', 'password1'), ('user2', 'password2'), ('user3', 'password3'), " +
                    "('user4', 'password4'), ('user5', 'password5'), ('user6', 'password6'), " +
                    "('user7', 'password7'), ('user8', 'password8'), ('user9', 'password9'), " +
                    "('user10', 'password10')";
            int userRows = stmt.executeUpdate(sqlInsertUsers);
            System.out.println(userRows + "개의 글이 Users 테이블에 생성되었습니다.");

            String sqlInsertPosts = "INSERT INTO posts (image, message, user_id) VALUES " +
                    "(NULL, 'Hello World', 1), (NULL, 'Learning Java', 2), " +
                    "(NULL, 'At the beach', 3), (NULL, 'Eating pizza', 4), " +
                    "(NULL, 'Watching a movie', 5), (NULL, 'At a concert', 6), " +
                    "(NULL, 'Playing games', 7), (NULL, 'Reading a book', 8), " +
                    "(NULL, 'Visiting museums', 9), (NULL, 'Going hiking', 10)";
            int postRows = stmt.executeUpdate(sqlInsertPosts);
            System.out.println(postRows + "개의 글이 posts 테이블에 생성되었습니다.");

            String sqlInsertComments = "INSERT INTO post_comments (comment, user_id, post_id) VALUES " +
                    "('Nice post!', 1, 1), ('Love this!', 2, 1), ('So cool!', 3, 2), " +
                    "('Wow!', 4, 3), ('Great pic!', 5, 3), ('Can\\'t agree more!', 6, 4), " +
                    "('LOL', 7, 5), ('That\\'s awesome!', 8, 6), ('Yummy!', 9, 7), ('Interesting!', 10, 8)";
            int commentRows = stmt.executeUpdate(sqlInsertComments);
            System.out.println(commentRows + "개의 글이 posts_comment 테이블에 생성되었습니다.");

            String sqlInsertLikes = "INSERT INTO post_likes (user_id, post_id) VALUES " +
                    "(1, 1), (2, 1), (3, 1), (4, 2), (5, 2), " +
                    "(6, 3), (7, 3), (8, 4), (9, 5), (10, 5)";
            int likeRows = stmt.executeUpdate(sqlInsertLikes);
            System.out.println(likeRows + "개의 글이 post_likes 테이블에 생성되었습니다.");

            String sqlInsertFollows = "INSERT INTO follow_follower (follower_id, user_id) VALUES " +
                    "(1, 2), (1, 3), (2, 3), (2, 4), (3, 4), " +
                    "(3, 5), (4, 5), (4, 6), (5, 6), (5, 7)";
            int followRows = stmt.executeUpdate(sqlInsertFollows);
            System.out.println(followRows + "개의 글이 follow_follower 테이블에 생성되었습니다.");

            String sqlInsertHashtags = "INSERT INTO hashtags (name) VALUES " +
                    "('summer'), ('java'), ('beach'), ('pizza'), ('movie'), " +
                    "('concert'), ('games'), ('book'), ('museum'), ('hiking')";
            int hashtagRows = stmt.executeUpdate(sqlInsertHashtags);
            System.out.println(hashtagRows + "개의 글이 hashtags 테이블에 생성되었습니다.");

            String sqlInsertPostsHashtags = "INSERT INTO posts_hashtags (hashtag_id, post_id) VALUES " +
                    "(1, 1), (2, 2), (3, 3), (4, 4), (5, 5), " +
                    "(6, 6), (7, 7), (8, 8), (9, 9), (10, 10)";
            int postHashtagRows = stmt.executeUpdate(sqlInsertPostsHashtags);
            System.out.println(postHashtagRows + "개의 글이 posts_hashtags 테이블에 생성되었습니다.");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

- 문제 

1. 모든 사용자의 이름과 패스워드를 조회하시오.

package instagramref;

import java.sql.*;

public class Example01 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "SELECT username, password FROM Users";
        ResultSet rs = statement.executeQuery(SQL);

        while(rs.next()) {
            System.out.println(rs.getString("username") + " " +
                    rs.getString("password"));
        }
    }
}

 

2. 모든 게시글의 메시지와 생성 시간을 조회하시오.

package instagramref;

import java.sql.*;

public class Example02 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "SELECT message, created_at FROM Posts";
        ResultSet rs = statement.executeQuery(SQL);

        while(rs.next()) {
            System.out.println(rs.getString("message") + " " +
                    rs.getString("created_at"));
        }
    }
}

 

3. 게시글이 1개 이상 있는 모든 사용자의 이름을 조회하시오.

package instagramref;

import java.sql.*;

public class Example03 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "SELECT distinct u.username FROM users u " +
                "JOIN posts p " +
                "ON u.id = p.user_id ";
        ResultSet rs = statement.executeQuery(SQL);

        while(rs.next()) {
            System.out.println(rs.getString("username"));
        }
    }
}

 

4. 최근 24시간 내에 생성된 게시글의 메시지를 조회하시오.

package instagramref;

import java.sql.*;

public class Example04 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "SELECT message FROM Posts " +
                "WHERE created_at >= CURRENT_TIMESTAMP - INTERVAL 1 DAY";
        ResultSet rs = statement.executeQuery(SQL);

//        rs.last();
//        int length = rs.getRow();
//        rs.beforeFirst();
//        System.out.println(length);
        int count = 0;
        while(rs.next()) {
            System.out.println(rs.getString("message"));
            count++;
        }

        System.out.println(count);
    }
}

 

5. 모든 사용자의 이름과 그들의 게시글 수를 조회하시오.

package instagramref;

import java.sql.*;

public class Example05 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "SELECT u.username as username , COUNT(p.id) AS post_count " +
                "FROM Users as u " +
                "LEFT JOIN Posts as p ON u.id = p.user_id " +
                "GROUP BY u.username";
        ResultSet rs = statement.executeQuery(SQL);

        while(rs.next()) {
            System.out.println(rs.getString("username") + " " +
                    rs.getString("post_count"));
        }
    }
}

 

6. 'like'가 포함된 게시글 메시지를 조회하시오.

package instagramref;

import java.sql.*;

public class Example06 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "SELECT message FROM Posts " +
                "WHERE message LIKE '%like%'";
        ResultSet rs = statement.executeQuery(SQL);

        while(rs.next()) {
            System.out.println(rs.getString("message"));
        }
    }
}

 

7. 게시글 중 좋아요가 5개 이상인 게시글의 메시지를 조회하시오.

package instagramref;

import java.sql.*;

public class Example07 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "SELECT p.id as id, COUNT(pl.id) as count FROM Posts as p " +
                "JOIN post_likes as pl " +
                "ON pl.post_id = p.id " +
                "GROUP BY p.id " +
                "HAVING count >= 5";
        ResultSet rs = statement.executeQuery(SQL);

        while(rs.next()) {
            System.out.println(rs.getString("id") + " " + rs.getInt("count"));
        }
    }
}

 

8. 각 게시글에 대한 총 댓글 수를 조회하시오.

package instagramref;

import java.sql.*;

public class Example08 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "SELECT ff.follower_id , count(*) " +
                "FROM follow_follower ff " +
                "GROUP BY ff.follower_id " +
                "HAVING COUNT(*) = (SELECT MAX(cnt) from ( " +
                "SELECT count(*) as cnt " +
                "FROM follow_follower ff " +
                "GROUP by ff.follower_id " +
                ") as sq)";
        ResultSet rs = statement.executeQuery(SQL);

        while(rs.next()) {
            System.out.println(rs.getString("ff.follower_id") + " " + rs.getInt("count(*)"));
        }
    }
}

 

9. 가장 많은 팔로워를 가진 사용자의 이름을 조회하시오.

package instagramref;

import java.sql.*;

public class Example09 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "SELECT ff.follower_id , count(*) " +
                "FROM follow_follower ff " +
                "GROUP BY ff.follower_id " +
                "HAVING count(*) = (SELECT MAX(cnt) from ( " +
                "SELECT count(*) as cnt " +
                "FROM follow_follower ff " +
                "GROUP BY ff.follower_id " +
                ") as sq)";
        ResultSet rs = statement.executeQuery(SQL);

        while(rs.next()) {
            System.out.println(rs.getString("ff.follower_id") + " " + rs.getInt("count(*)"));
        }
    }
}

 

10. 특정 사용자의 이름을 변경하시오. 예를 들어, 사용자 'user1'의 이름을 'newUser1'로 변경하시오.

package instagramref;

import java.sql.*;

public class Example10 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "UPDATE Users SET username = 'newUSer1' WHERE username = 'user1'";
        statement.executeUpdate(SQL);

//        while(rs.next()) {
//            System.out.println(rs.getString("ff.follower_id") + " " + rs.getInt("count(*)"));
//        }
    }
}

 

11. 게시글의 좋아요 수를 증가시키는 쿼리를 작성하시오. 예를 들어, 게시글 ID가 3인 게시글의 좋아요 수를 5 증가시키시오.

package instagramref;

import java.sql.*;

public class Example11 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "INSERT INTO post_likes (user_id, post_id) VALUES " +
                "(6, 3), (7, 3), (8, 3), (9, 3), (2, 3);";
        int count = statement.executeUpdate(SQL);

        System.out.println(count);
//        while(rs.next()) {
//            System.out.println(rs.getString("ff.follower_id") + " " + rs.getInt("count(*)"));
//        }
    }
}

 

12. 특정 사용자의 모든 게시글의 메시지에 추가 텍스트를 삽입하시오. 예를 들어, 사용자 ID가 2인 사용자의 모든 게시글에 " - updated"를 메시지 끝에 추가하시오.

package instagramref;

import java.sql.*;

public class Example12 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "UPDATE Posts SET message = " +
                "CONCAT(message, ' - updated') " +
                "WHERE user_id = 2";
        int count = statement.executeUpdate(SQL);

        System.out.println(count);
//        while(rs.next()) {
//            System.out.println(rs.getString("ff.follower_id") + " " + rs.getInt("count(*)"));
//        }
    }
}

 

13. 사용자가 작성한 모든 글의 message를 업데이트하시오. 예를 들어, 사용자 ID가 4인 사용자가 작성한 message를 'hello world'로 변경하시오.

package instagramref;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class Example13 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement statement = conn.createStatement();

        String SQL = "UPDATE Posts SET message = " +
                "'hello world' " +
                "WHERE user_id = 4";
        int count = statement.executeUpdate(SQL);

        System.out.println(count);
//        while(rs.next()) {
//            System.out.println(rs.getString("ff.follower_id") + " " + rs.getInt("count(*)"));
//        }
    }
}

 

14. 특정 게시글의 생성 날짜를 현재 날짜와 시간으로 업데이트하시오. 예를 들어, 게시글 ID가 1인 게시글의 생성 날짜를 현재 날짜와 시간으로 업데이트하시오.

package instagramref;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class Example14 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String user = "root";
        String password = "11";

        Connection conn = DriverManager.getConnection(URL, user, password);
        Statement stmt = conn.createStatement();

        String SQL = "UPDATE Posts SET message = " +
                "CURRENT_TIMESTAMP " +
                "WHERE id = 1";
        int count = stmt.executeUpdate(SQL);

        System.out.println(count);
//        while (rs.next()) {
//            System.out.println(rs.getString("p.id") + " " + rs.getInt("COUNT(pc.id)"));
//        }
    }
}

 

15. 특정 사용자의 모든 게시글을 삭제하시오. 예를 들어, 사용자 ID가 5인 사용자의 모든 게시글을 삭제하시오.

package instagramref;

import java.sql.*;

public class Example15 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String user = "root";
        String password = "11";

        Connection conn = DriverManager.getConnection(URL, user, password);
        Statement stmt = conn.createStatement();

        String SQL = "DELETE FROM Posts WHERE user_id = 5";
    }
}

 

16. 특정 사용자를 삭제하시오. 이 때, 관련된 모든 게시글, 댓글, 좋아요, 팔로우 정보도 함께 삭제하시오. 예를 들어, 사용자 ID가 10인 사용자와 그의 관련 데이터를 모두 삭제하시오.

package instagramref;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class Example16 {
    public static void main(String[] args) throws SQLException {

        String URL = "jdbc:mysql://127.0.0.1:3306/instagram";
        String USER = "root";
        String PASSWORD = "11";

        Connection conn = DriverManager.getConnection(URL, USER, PASSWORD);
        Statement stmt = conn.createStatement();

        String SQL = "DELETE FROM Users WHERE id = 10";
        int count = stmt.executeUpdate(SQL);

        System.out.println(count);
    }
}