Database Normalization and Nested Lists -- Cannot Think of a Solution

I am trying to implement a system on my website similar to that of Facebook's "Like" feature. Where users can click a button which counter++'s. However, I have run into a problem in terms of efficiently storing data into my DB.

Each story has it's own row in the stories table in my DB with the columns like and users_like.

I want each person to only be able to like the story once. Therefore I need to somehow store data that shows that the user has, in fact, like++'d the post.

All I could thing of was to have a column named users_like and then add each user, fol开发者_JAVA百科lowed by a comma, to the column using CONCAT and then using the php function to explode the data.

However, this method, as far as I know, is in the opposite direction of database normalization.

What is the best way to do this and I understand "best" is subjective.

I cannot add a liked flag to the user table because there will be a vast number of stories the person could 'like.'

Thanks

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You need a many to many table in your database that will store a foreign key to the stories table and a foreign key to the user table. You put a constraint on this table saying that the story fk - user fk combo must be unique.

You now don't even have to have a like column, you just count the number of rows in the many to many table corresponding to your story.