Question

Hi I have a question regarding a method to prevent second voting in a website where people can vote up or vote down a comment. Like Stackoverflow!! 🙂

The question is how I can keep track of whether a comment has already been voted by a logged in user. Lets assume this is for a online ecommerce store with reviews on products. Here’s what I think:

• All reviews data is stored in a table called ‘reviews’
• Field names: review_id, product_id, user_id, title, description, time_created, up_votes, down_votes, up_voters, down_voters
• up_votes and down_votes contain the number of votes voting it up or down
• up_voters and down_voters contain the user_id of the people who voted up or down in the format 1101.1102.1103 for users with user_id 1101, 1102 and 1103.

When a person clicks on the up vote button, the system will check if the current user’s user_id matches anyone in up_voters. An explode function will turn 1101.1102.1103 into an array and in_array() will be used to check if the user has already voted.

Is there a better way to go about doing this?

Answer 1

That table will give you nightmares down the line. Just think of a hit product with 1K up_voters, your field will be 10K*4 characters long! Not just that, it will hinder your ability to make reports and study the data etc.

I don’t know much about your needs but from what I can see in your table, I’d suggest the below.

review
user_id, product_id, type_of_vote, title, description, time_created

Use above table and use user_id, product_id as the key

OR

review
review_id, product_id, title, description, time_created

vote
review_id, user_id, type_of_vote

There are n number of ways to design tables for this. If it is an Operational Data Store(ODS) then you might want to normalize your design. If it’s a warehouse then you may consider first table I mentioned above.