var mysql = require('mysql')

var con = mysql.createConnection({
    host: !host,
    database: !database,
    user: !username,
    password: !pass
})

con.connect(function() {
    con.query('SELECT * FROM table WHERE (some condition that is unique to your record)', function(data) {
        if(data.length > 0) {
            // do something
        }
        else {
            // do something else
        }
    })
})