So I'm trying to implement a like button for images on my site. But I'm having a little trouble figuring out how it goes.

So far, I have this on the SQLI side of things :
CREATE TABLE if not exists `likes` (
             `id` int(11) NOT NULL AUTO_INCREMENT,
             `liked_image_id` varchar(300) NOT NULL,
             `liker_username` varchar(50) NOT NULL,
              `liked_unliked` enum('0','1') NOT NULL, DEFAULT '0'
               PRIMARY KEY (`id`)
Where `id` is the id of the like,
`liked_image_id` is the id of the image being liked,
`liker_username` is the username of the user clicking the like button,
`liked_unliked` is whether or not that user has liked the image (1 for liked, 0 for unliked [to make sure users only vote once]). what I have so far even correct? Like I said, I'm trying to get it so that users can click the like button and like image, but only once. Any help is appreciated. Thanks