Скачать или смотреть How to Fetch Values from Multiple Tables in CodeIgniter Efficiently

Discover how to elegantly retrieve data from multiple related tables in CodeIgniter, using effective queries for better performance and readability.
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This video is based on the question https://stackoverflow.com/q/63923461/ asked by the user 'Sheetal Sharma' ( https://stackoverflow.com/u/14023296/ ) and on the answer https://stackoverflow.com/a/63925526/ provided by the user 'KUMAR' ( https://stackoverflow.com/u/12030528/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fetching Values from Multiple Tables in CodeIgniter: A Guide

When working with databases in CodeIgniter, you may often need to retrieve values from multiple tables. In this guide, we are going to explore a common issue faced while fetching values from two tables—Homework and Deliveries. This challenge arises especially when both tables share a common field, such as student_id. Let’s break down the problem and provide a clear solution.

Understanding the Problem

In our scenario, you need to fetch the title field from the homework table while already fetching the homework_code from the deliveries table, both linked through the student_id. The original attempt showed discrepancies in the query that prevented the retrieval of the expected results.

Database Structure

Before diving into the solution, let’s take a quick look at the structure of the two tables involved:

Homework Table

[[See Video to Reveal this Text or Code Snippet]]

Deliveries Table

[[See Video to Reveal this Text or Code Snippet]]

The Original Code Issues

Here is the part of the code that needs modification:

[[See Video to Reveal this Text or Code Snippet]]

The line that attempts to fetch the title from homework using homework_code is ineffective given that homework_code is not linked directly to title through the row data.

Proposed Solution

To correctly fetch the title from the homework table while iterating over the deliveries, a modification is necessary. Here’s how you should refactor the code:

Updated Code

Replace the problematic section with the following:

[[See Video to Reveal this Text or Code Snippet]]

Explanation:

Extract student_id: First, we extract the student_id from the current $row2 iterating over invoices.

Update the Query: Utilize this student_id to query the homework table correctly. This ensures you fetch the right title related to the student.

Display the Result: Finally, echo the title fetched from the homework table.

Why This Works:

By querying homework based on student_id, we maintain the relationship between Deliveries and Homework, resulting in accurate data retrieval.

This approach provides better readability and performance by preventing the retrieval of unnecessary data from the database.

Conclusion

Understanding how to work with multiple tables in CodeIgniter is essential for effective database management in your applications. By applying the right queries, you can retrieve the information you need efficiently while maintaining a clean and organized code structure.

Remember to always ensure your database relationships are properly understood when performing queries to get the most out of your data.

Happy coding and don't hesitate to reach out for more tips on CodeIgniter or database management!