How to delete a row of data using SQL language

SQL language to delete a certain row JavaScript

During the process of data interaction, data often needs to be deleted, which is especially common in database operations. Using SQL language to delete data is also very simple. This article will introduce how to use SQL language to delete a certain row of data and implement it with JavaScript code.

SQL Language Introduction

SQL is the abbreviation of Structured Query Language (Structured Query Language) and is a standard interactive language used to manage relational database management systems (RDBMS). SQL language is used to perform various operations in the database such as querying, inserting, updating and deleting data.

The syntax format for deleting data is as follows:

DELETE FROM table_name WHERE condition;

Among them, table_name is the name of the table where the data is to be deleted, and condition is the condition that specifies the data to be deleted. For example, to delete data whose Age is greater than 20 in the Customer table, you can use the following statement:

DELETE FROM Customer
WHERE Age > 20;

After executing this statement, the data that meets the conditions will be deleted. Either all or none are deleted, depending on whether the conditions in the WHERE clause match the data in the table.

JavaScript implementation of deleting data

When using JavaScript to delete data, you need to use back-end languages ​​​​(such as PHP, Python, Node.js, etc.) to execute SQL statements. In this article, we will use Node.js as an example to delete data using SQL language.

Before starting, you need to install the relevant dependencies, as follows:

1. Install MySQL

brew install mysql

2. Install the mysql module

npm install mysql

After the installation is complete, you can connect to the MySQL database and execute SQL statements in JavaScript code. The following code demonstrates how to use JavaScript to connect to MySQL and delete data that meets the conditions:

const mysql = require('mysql')

// 创建数据库连接
const connection = mysql.createConnection({
  host: 'localhost',
  user: 'root',
  password: 'password',
  database: 'test_db'
})

// 执行 SQL 语句
connection.query('DELETE FROM test_table WHERE age > 18', (err, result) => {
  if (err) {
    console.log('执行 SQL 语句失败：', err.message)
  } else {
    console.log(`删除成功，删除了 ${result.affectedRows} 条数据`)
  }
})

The mysql module in the code provides a method to connect to the database and execute SQL statements, among which createConnection This method is used to create a database link and replace the configuration with your own database configuration. The query method is used to execute SQL statements. The first parameter is the SQL statement to be executed. The second parameter is the callback function. When the execution is completed, the function will be called. The first parameter of the callback function is The first parameter is the error message of executing the SQL statement, and the second parameter is the result of successful execution.

When the execution is successful, a result object containing the affectedRows attribute will be returned, indicating the number of deleted rows.

Summary

This article introduces how to use SQL language to delete a certain row of data and implement it with JavaScript code. I hope it will be helpful to readers. In actual development, you need to pay attention to security issues such as SQL injection to avoid data leakage.

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