MySQL - 删除查询

要通过 Node.js 程序删除数据库表中的数据，需要使用 mysql2 库的 query() 函数执行 DELETE 语句，如下所示：

sql = "DELETE FROM table_name [WHERE Clause]";
VALUES (value1, value2, value3,...valueN)"
con.query(sql);

要通过 Java 程序删除数据库表中的数据，需要使用 JDBC 函数 executeUpdate() 执行 DELETE 语句，如下所示：

String sql="DELETE FROM table_name [WHERE Clause]";
statement.executeUpdate(sql);

要通过 Python 程序删除数据库表中的数据，需要使用 MySQL Connector/Python 的 execute() 函数执行 DELETE 语句，如下所示：

delete_query = "DELETE FROM table_name [WHERE Clause]"
cursorObj.execute(delete_query);

var mysql = require('mysql2');
var con = mysql.createConnection({
    host: "localhost",
    user: "root",
    password: "Nr5a0204@123"
});

  //Connecting to MySQL
  con.connect(function (err) {
  if (err) throw err;
  console.log("Connected!");

  //Selecting a Database
  sql = "USE TUTORIALS"
  con.query(sql);

  //Updating a single record in the table
  sql = "DELETE FROM tutorials_tbl WHERE tutorial_id = 5;"
  con.query(sql);

  //Selecting records from table
  sql = "SELECT * FROM tutorials_tbl"
  con.query(sql, function (err, result) {
      if (err) throw err;
      console.log(result);
  });
});

输出

生成的输出如下 -

Connected!
[
  {
    tutorial_id: 1,
    tutorial_title: 'Learn PHP',
    tutorial_author: 'John Paul',
    submission_date: 2023-07-25T18:30:00.000Z
  },
  {
    tutorial_id: 2,
    tutorial_title: 'Learn MySQL',
    tutorial_author: 'Abdul S',
    submission_date: 2021-03-27T18:30:00.000Z
  },
  {
    tutorial_id: 3,
    tutorial_title: 'Learning Java',
    tutorial_author: 'Sanjay',
    submission_date: 2007-05-05T18:30:00.000Z
  },
  {
    tutorial_id: 4,
    tutorial_title: 'Python Tutorial',
    tutorial_author: 'Sasha Lee',
    submission_date: 2016-09-03T18:30:00.000Z
  }
]

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
public class DeleteQuery {
	public static void main(String[] args) {
		String url = "jdbc:mysql://127.0.0.1:3306/TUTORIALS";
		String user = "root";
		String password = "password";
		ResultSet rs;
		try {
			Class.forName("com.mysql.cj.jdbc.Driver");
            Connection con = DriverManager.getConnection(url, user, password);
            Statement st = con.createStatement();
            //System.out.println("Database connected successfully...!");
            String sql = "DELETE FROM tutorials_tbl WHERE tutorial_id = 6";
            st.executeUpdate(sql);
            System.out.println("Delete query executed successfully..!");
            String sql1 = "SELECT * FROM tutorials_tbl";
            rs = st.executeQuery(sql1);
            System.out.println("Table records: ");
            while(rs.next()) {
            	String tutorial_id = rs.getString("tutorial_id");
            	String tutorial_title = rs.getString("tutorial_title");
            	String tutorial_author = rs.getString("tutorial_author");
            	String submission_date = rs.getString("submission_date");
            	System.out.println("Id: " + tutorial_id + ", Title: " + tutorial_title + ", Author: " +  tutorial_author + ", Submission_date: " + submission_date);
            }
		}catch(Exception e) {
			e.printStackTrace();
		}
	}
}

输出

获得的输出如下所示 -

Delete query executed successfully..!
Table records: 
Id: 1, Title: Learn PHP, Author: John Paul, Submission_date: 2023-08-08
Id: 2, Title: Angular Java, Author: Abdul S, Submission_date: 2023-08-08
Id: 3, Title: Learning Java, Author: Sanjay, Submission_date: 2007-05-06
Id: 4, Title: Python Tutorial, Author: Sasha Lee, Submission_date: 2016-09-04
Id: 5, Title: Hadoop Tutorial, Author: Chris Welsh, Submission_date: 2023-08-08

import mysql.connector
import datetime
#establishing the connection
connection = mysql.connector.connect(
    host='localhost',
    user='root',
    password='password',
    database='tut'
)
#Creating a cursor object 
cursorObj = connection.cursor()
delete_query = "DELETE FROM tutorials_tbl WHERE tutorial_id = 6"
cursorObj.execute(delete_query)
connection.commit()
print("Row deleted successfully.")
cursorObj.close()
connection.close()

输出

以下是上述代码的输出 -

Row deleted successfully.