var codes = generateUniqueCodes(10000000);
var query = printQuery(codes);
console.log(query);

function unique(arr) {
 var sorted = arr;
    sorted.sort();
    return sorted.filter(function(value, index, arr){
        if(index < 1)
            return true;
        else
            return value != arr[index-1];
    });
}



function printQuery(codes) {
	var query = 'INSERT INTO referral_code(code) VALUES '

	for(var i = 0; i < codes.length; i++) {
		query += '(\'RF' + codes[i] + '\'),';
	}
	return query.substring(0,query.length - 1) + ';';
}

function generateUniqueCodes(n) {
	var codes = [];

	for (var i = 1; i <= n; i++) {
		codes.push(generate(5));
	}

	//codes = codes.filter(onlyUnique);

	return unique(codes);
}

function generate(limit) {
	var dictionary = 'qwertyuiopasdfghjklzxcvbnm1234567890';
	var maxOffset = dictionary.length;
	var code = '';

	for (var length = limit; length > 0; length--) {
        code += dictionary[Math.floor(Math.random() * maxOffset)];
    }

    return code;
}

function onlyUnique(value, index, self) {
    return self.indexOf(value) === index;
}