


How to Prevent Multiple Votes in a Comment Rating System Without Storing Arrays in MySQL?
Oct 31, 2024 am 02:35 AMStoring Arrays in MySQL: An Alternative Approach
To prevent multiple votings in a comment rating system, you wish to store an array of user IDs in a MySQL field. While this is not directly supported by MySQL, consider the following alternative approach:
Database Schema
Create three tables:
- comments: Contains comment IDs and bodies.
- users: Stores user IDs and usernames.
- comments_votes: Links comments to users who have voted on them, including the vote type.
CREATE TABLE comments ( comment_id int, body varchar(100), PRIMARY KEY (comment_id) ); CREATE TABLE users ( user_id int, username varchar(20), PRIMARY KEY (user_id) ); CREATE TABLE comments_votes ( comment_id int, user_id int, vote_type int, PRIMARY KEY (comment_id, user_id) );
Example Data
INSERT INTO comments VALUES (1, 'first comment'); INSERT INTO comments VALUES (2, 'second comment'); INSERT INTO users VALUES (1, 'user_a'); INSERT INTO users VALUES (2, 'user_b'); INSERT INTO comments_votes VALUES (1, 1, 1); INSERT INTO comments_votes VALUES (2, 1, 1);
Checking for User Eligibility
To determine if a user has already voted on a particular comment, use a simple query:
SELECT COUNT(*) FROM comments_votes WHERE comment_id = <comment id> AND user_id = <user id>;
This approach prevents multiple votes as the primary key constraint on the comments_votes table ensures uniqueness.
Preventing Multiple Votes
If the user has already voted, disable the voting icons in the system logic based on the query result.
Advantages of This Approach
- Ensures data integrity through foreign key constraints.
- Avoids the need to serialize arrays into a single field.
- Simplifies database operations and reduces the risk of data corruption.
The above is the detailed content of How to Prevent Multiple Votes in a Comment Rating System Without Storing Arrays in MySQL?. For more information, please follow other related articles on the PHP Chinese website!

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