Android SQL - Check if whole row already exists in database

I'm trying to create a simple favorites application, where you can keep your favorites pages (from the web for example).

Let's say I have the following data in my database

Title    | URL     | TAG      |
-------------------------------
Hey       Ho.com    Site
Jo        Jo.com    Image
Jo        Mo.com    Image

Now I want to make sure, the user does not add the same page twice, so I will check if the value already exists. But I need to that the user does not add a site to the table that has already been added.

So let's say I would try to add:

Title    | URL     | TAG      |
-------------------------------
Jo        Mo.com    Image

This it would return true (for "check if row exist", because an identical row already exists).

But if I would try to add:

Title    | URL     | TAG      |
-------------------------------
Jo        Go.com    Image

It would return false (though the title already exists), because there is no identical row.

This is the code where I add my data to the database with:

public long createNote(String title, String url, String rn) {
    ContentValues initialValues = new ContentValues();
    initialValues.put(KEY_TITLE, title);
    initialValues.put(KEY_URL, url);
    initialValues.put(KEY_RN, rn);

    return mDb.insert(DATABASE_TABLE, null, initialValues);

How can I check if a row already exists in a database?