Скачать или смотреть Solving the Problem: How to Add 2 Different Queries in PHP

Discover the solution to display multiple SQL queries in PHP while avoiding common pitfalls. Learn how to manage multiple fetching variables correctly.
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This video is based on the question https://stackoverflow.com/q/62261136/ asked by the user 'lilin' ( https://stackoverflow.com/u/11993676/ ) and on the answer https://stackoverflow.com/a/62261398/ provided by the user 'Ford Prefect' ( https://stackoverflow.com/u/6903109/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Add 2 Different Queries in PHP

When working with PHP and MySQL, many developers encounter issues when trying to display data from multiple SQL queries on a single page. This is a common problem and can be quite frustrating, especially if your page is not showing data as you expect. In this article, we'll explore a solution to this problem using an example scenario where we want to display a list of students and allow a lecturer to add students under their care.

The Problem

The original issue arises when a code snippet is executed that fetches student data from the student table and simultaneously attempts to fetch supervisor data from the supervisor table. The key confusion comes from the use of the same variable to store results from both queries. Let's break down the situation a little more.

Original Code Breakdown

In the provided code:

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

The first query fetches the student data and stores it in $fetch.

Once the second query is executed to retrieve supervisor data, the $fetch variable is overwritten, losing the reference to the student data.

As a result, the output only displays the last fetched row which is from the supervisor table.

This highlights the key problem: using the same variable for both queries causes data loss.

The Solution

To resolve this problem, we can simply use different variables for each query result. This ensures that data from both queries can coexist without conflict.

Use Different Variables: For instance, use $fetch for the student data and $fetch2 for the supervisor data.

Code Update: Here's how you can modify your code:

Revised Code Snippet

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

Advantages of this Approach

Data Consistency: By using different variables, you maintain the integrity of both datasets.

Flexibility: You can now operate on each dataset independently, thus increasing your control over the output and functionality.

Ease of Maintenance: With a clearer structure, future developers (including yourself) will find it easier to manage and modify the code.

Conclusion

Managing multiple SQL queries in PHP can seem tricky, but with careful variable management, the process can become much simpler. By ensuring that you use distinct variable names for fetching data from multiple queries, you can avoid common pitfalls that lead to data loss or incorrect display.

By applying the solution outlined above, you'll find that displaying data from both the student and supervisor tables is straightforward, and your code will run more effectively. Happy coding!