Introduction to MySQL JSON_ARRAY_APPEND with Javascript

MySQL JSON_ARRAY_APPEND is a MySQL function that is used to append a value to a JSON array. This function can be used to manipulate and modify JSON data in MySQL.

In Javascript, you can use the mysql2 package to perform database operations, including calling MySQL functions like JSON_ARRAY_APPEND.

Syntax

The syntax of the MySQL JSON_ARRAY_APPEND function is as follows:

JSON_ARRAY_APPEND(json_doc, path, val)

• json_doc: The JSON document that you want to modify.
• path: The path to the JSON array that you want to append the value to. This is a string that can contain dot-separated keys and brackets for array indexes.
• val: The value that you want to append to the JSON array.

Example

Here's an example of how you can use the JSON_ARRAY_APPEND function in Javascript with the mysql2 package:

const mysql = require('mysql2/promise');

// create the connection pool
const pool = mysql.createPool({
    host: 'localhost',
    user: 'root',
    database: 'mydb'
});

// execute the query
async function myQuery() {
    const conn = await pool.getConnection();
    try {
        const userId = 123;
        const bookId = 456;
        const jsonString = '[{"userId":123,"books":[456]}]';
        const query = `SELECT JSON_ARRAY_APPEND('${jsonString}', '$[0].books', ${bookId}) AS new_json_string`;

        const [rows] = await conn.query(query);
        console.log(rows[0].new_json_string);
    } catch (err) {
        console.error(err);
    } finally {
        conn.release(); // release the connection
    }
}

In this example, we are appending the book ID 456 to the books array in the JSON string [{"userId":123,"books":[456]}]. The resulting JSON string will be '[{"userId":123,"books":[456,456]}]'.

Conclusion

MySQL JSON_ARRAY_APPEND is a powerful function that allows you to manipulate JSON data in MySQL. Using this function with Javascript and the mysql2 package, you can easily perform database operations and modify your JSON data.