How to close database connection in node.js?

Question

When i am closing database connection in node.js i am getting this error

Cannot enqueue Query after invoking quit.

Here is my code

socket.on('adminConnect', function (email) {
    connection = mysql.createConnection(db_config); // db_config has all details of database
    connection.connect(); // no problem in connection
    connection.query("SELECT id FROM user WHERE  email = '" + email + "' ", function (err, results, fields) {
        if (err) throw err;
        if (results[0]) {
            // Some code
            connection.end(); // its giving error "Cannot enqueue Query after invoking quit."
        } else {
            console.log("no id");
        }
    });
});

Answer 1

In general, you reuse connections instead of opening/closing all the time.

To answer your question, this is how:

connection.end();

Try putting the line outside the callback, because all the queries must complete before ending a connection, so you're safe like this:

connection.query(.......);
connection.end();

Your code would then be:

socket.on('adminConnect', function (email) {
    connection = mysql.createConnection(db_config); // db_config has all details of database
    connection.connect(); // no problem in connection
    connection.query("SELECT id FROM user WHERE  email = '" + email + "' ", function (err, results, fields) {
        if (err) throw err;
        if (results[0]) {
            // Some code
        } else {
            console.log("no id");
        }
    });
    connection.end();
});