How to implement data type conversion function in TypeScript using MySQL

How to use MySQL to implement data type conversion function in TypeScript

Introduction:
When developing web applications, data type conversion is a very common requirement. When processing data stored in a database, especially when using MySQL as the back-end database, we often need to convert the data in the query results to the type we require. This article will introduce how to use MySQL to implement data type conversion in TypeScript and provide code examples.

1. Preparation:
Before you start, make sure you have installed TypeScript and MySQL and are familiar with their basic usage.

2. Use TypeScript to connect to the MySQL database:
First, we need to use TypeScript to connect to the MySQL database. We can use the third-party library mysql2 to achieve this. First, install the mysql2 library in the project:

npm install mysql2

Next, we introduce the mysql2 module into the TypeScript code and configure the database connection:

import mysql from 'mysql2';

const connection = mysql.createConnection({
  host: 'localhost',
  user: 'your_username',
  password: 'your_password',
  database: 'your_database'
});

connection.connect((err) => {
  if (err) {
    console.error('Error connecting to MySQL database:', err);
    return;
  }
  console.log('Connected to MySQL database!');
});

The above code will connect to the local MySQL database and output information about successful connection.

3. Implement the data type conversion function:

1. Convert to string type:
   Sometimes, the results returned from the database query are of numeric type. But we need to convert it to string type. We can use the toString() method to achieve:

   connection.query('SELECT * FROM users', (err, rows) => {
     if (err) {
    console.error('Error executing query:', err);
    return;
     }
     rows.forEach((row) => {
    const id = row.id.toString(); // 将id字段转换为字符串类型
    // 在此处继续处理数据...
     });
   });

2. Convert to numeric type:
   Similarly, sometimes we need the string type obtained from the database query results Data is converted to numeric type. We can use the Number() method to achieve:

   connection.query('SELECT * FROM products', (err, rows) => {
     if (err) {
    console.error('Error executing query:', err);
    return;
     }
     rows.forEach((row) => {
    const price = Number(row.price); // 将price字段转换为数字类型
    // 在此处继续处理数据...
     });
   });

3. Convert to date type:
   When the database stores date or time type data, we often need to convert it For JavaScript Date type. We can use the new Date() constructor to achieve this:

   connection.query('SELECT * FROM orders', (err, rows) => {
     if (err) {
    console.error('Error executing query:', err);
    return;
     }
     rows.forEach((row) => {
    const orderDate = new Date(row.order_date); // 将order_date字段转换为日期类型
    // 在此处继续处理数据...
     });
   });

4. Summary:
This article introduces how to use MySQL to implement data type conversion in TypeScript. Through the sample code, we learned how to convert numeric type to string type, string type to numeric type, and string type to date type. I hope this knowledge will be helpful to you when dealing with database data type conversion in TypeScript development.

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