Database: Primary Key In Survey Related Tables
Introduction
In the context of survey-related tables, a primary key plays a crucial role in maintaining data integrity and consistency. However, when dealing with multiple survey records for a single user across various sessions, the traditional approach of using a single primary key can lead to conflicts and limitations. In this article, we will explore the problem of using a single primary key in survey-related tables and propose two potential solutions to address this issue.
Problem Statement
We currently have three tables for storing survey results: mentorship_preferences, lifestyle_answers, and enneagram_answers. Each of these tables uses user_id as the sole primary key, which restricts each user to only one survey record across all sessions. This approach presents a significant limitation, as a single user can apply to multiple mentorship sessions and must be able to submit a separate survey for each application.
The Issue with Single Primary Key
Using user_id as the primary key prevents inserting more than one record per user in each table, causing conflicts on second submissions. This limitation arises from the fact that a single primary key is used to uniquely identify each record in the table. When a user submits multiple surveys, the system cannot accommodate multiple records for the same user, leading to errors and inconsistencies.
Proposed Solution Options
To address the issue of using a single primary key in survey-related tables, we propose two potential solutions:
1. Tie Each Survey Table to the Corresponding Application Record
Solution Overview
Replace the user_id primary key with an application_id foreign key to the applications table. This approach ensures a one-to-one link between an application and its survey entries.
Benefits
- Ensures a one-to-one link between an application and its survey entries
- Allows for multiple survey records for a single user across various sessions
Implementation
To implement this solution, we need to make the following changes:
- Add an
application_idforeign key to thementorship_preferences,lifestyle_answers, andenneagram_answerstables - Update the primary key of each table to use the
application_idforeign key - Modify the application logic to create a new application record for each survey submission
Example Use Case
Suppose we have a user who applies to multiple mentorship sessions. We can create a new application record for each session and link the corresponding survey records to the application using the application_id foreign key.
2. Use a Composite Key of (session_id, user_id)
Solution Overview
Keep session_id and user_id in each survey table and make them the composite primary key. This approach allows one survey per user-session combination, but requires application logic to verify an existing application before insert.
Benefits
- Allows one survey per user-session combination
- Does not require a separate application table
Implementation
To implement this solution, we need to make the following changes:
- Add
session_idanduser_idto thementorship_preferences,lifestyle_answers, andenneagram_answers` tables - Make
session_idanduser_idthe composite primary key of each table - Modify the application logic to verify an existing application before inserting a new survey record
Example Use Case
Suppose we have a user who applies to multiple mentorship sessions. We can create a new survey record for each session, using the session_id and user_id as the composite primary key.
Conclusion
In conclusion, using a single primary key in survey-related tables can lead to conflicts and limitations when dealing with multiple survey records for a single user across various sessions. The proposed solutions, tying each survey table to the corresponding application record and using a composite key of (session_id, user_id), offer alternative approaches to address this issue. By choosing the most suitable solution, we can ensure data integrity and consistency in our survey-related tables.
Recommendations
Based on the proposed solutions, we recommend the following:
- Use the first solution, tying each survey table to the corresponding application record, when dealing with multiple survey records for a single user across various sessions.
- Use the second solution, using a composite key of
(session_id, user_id), when dealing with a single survey record per user-session combination.
Introduction
In our previous article, we discussed the problem of using a single primary key in survey-related tables and proposed two potential solutions. In this article, we will address some frequently asked questions (FAQs) related to the proposed solutions.
Q&A
Q: What is the main difference between the two proposed solutions?
A: The main difference between the two proposed solutions is that the first solution, tying each survey table to the corresponding application record, uses a foreign key to link the survey records to the application, while the second solution, using a composite key of (session_id, user_id), uses a composite primary key to link the survey records to the user-session combination.
Q: Which solution is more suitable for my use case?
A: The choice of solution depends on your specific use case. If you need to accommodate multiple survey records for a single user across various sessions, the first solution is more suitable. If you need to accommodate a single survey record per user-session combination, the second solution is more suitable.
Q: How do I implement the first solution?
A: To implement the first solution, you need to make the following changes:
- Add an
application_idforeign key to thementorship_preferences,lifestyle_answers, andenneagram_answerstables - Update the primary key of each table to use the
application_idforeign key - Modify the application logic to create a new application record for each survey submission
Q: How do I implement the second solution?
A: To implement the second solution, you need to make the following changes:
- Add
session_idanduser_idto thementorship_preferences,lifestyle_answers, andenneagram_answerstables - Make
session_idanduser_idthe composite primary key of each table - Modify the application logic to verify an existing application before inserting a new survey record
Q: What are the benefits of using a composite key?
A: The benefits of using a composite key include:
- Allows one survey per user-session combination
- Does not require a separate application table
Q: What are the benefits of using a foreign key?
A: The benefits of using a foreign key include:
- Ensures a one-to-one link between an application and its survey entries
- Allows for multiple survey records for a single user across various sessions
Q: How do I handle duplicate survey records?
A: To handle duplicate survey records, you can use a unique constraint on the session_id and user_id columns to prevent duplicate records from being inserted.
Q: How do I handle survey records with missing or invalid data?
A: To handle survey records with missing or invalid data, you can use data validation and error handling mechanisms to ensure that only valid data is inserted into the database.
Conclusion
In conclusion, the proposed solutions, tying each survey table to the corresponding application record and using a composite key of (session_id, user_id), offer alternative approaches to address the issue of using a single primary key in survey-related tables. By understanding the benefits and drawbacks of each, you can make an informed decision about which solution is best suited for your use case.
Recommendations
Based on the proposed solutions and FAQs, we recommend the following:
- Use the first solution, tying each survey table to the corresponding application record, when dealing with multiple survey records for a single user across various sessions.
- Use the second solution, using a composite key of
(session_id, user_id), when dealing with a single survey record per user-session combination. - Use a unique constraint on the
session_idanduser_idcolumns to prevent duplicate records from being inserted. - Use data validation and error handling mechanisms to ensure that only valid data is inserted into the database.