Скачать или смотреть How to Delete Entries from a SELECT Query Result in MySQL

Learn how to effectively delete entries from a SELECT query result in MySQL using inline views and proper syntax.
---
This video is based on the question https://stackoverflow.com/q/63021221/ asked by the user 'Optimus Servers' ( https://stackoverflow.com/u/13709041/ ) and on the answer https://stackoverflow.com/a/63022225/ provided by the user 'spencer7593' ( https://stackoverflow.com/u/107744/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: How to delete entries from a SELECT query result in mysql?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Delete Entries from a SELECT Query Result in MySQL

Deleting entries from a database can be a challenge, especially when trying to use the result of a SELECT query. In this post, we will delve into a common scenario where you might want to delete specific rows based on the result of a more complex query, and I'll guide you through the solution step-by-step.

Understanding the Problem

Imagine that you have a database for WordPress, specifically with tables for posts and translations. You want to delete certain product posts that are associated with a specific language code (e.g., 'es-es'). However, crafting an effective DELETE statement from a SELECT query result can be tricky. You might have tried a few different queries but met with syntax errors or unexpected results.

To illustrate, here’s a simplified version of the query you started with:

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

This query successfully retrieves the data you need to delete. The challenge lies in effectively converting this result set into a DELETE operation.

The Solution

Step 1: Create an Inline View

To delete entries based on the results of your SELECT query, you can use what's known as an inline view or derived table. This essentially means wrapping your SELECT query in parentheses and treating it as a separate table.

Here’s how you can structure this part:

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

In this query:

We’ve created an inline view (aliased as q) that contains the IDs of the posts you want to delete.

We join this view with the wp_posts table to select the rows that will ultimately be deleted.

Step 2: Verify the Results

Before proceeding to delete the rows, it’s wise to verify that this query returns the correct set of posts that you aim to remove. You can run the SELECT statement and review the returned rows carefully. If everything looks good, you can move on to the next step.

Step 3: Transform to DELETE Statement

Once you confirm that the SELECT is returning the desired results, converting it to a DELETE statement is straightforward. You simply replace the SELECT keyword with DELETE. Here’s the final version of your delete query:

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

Important Notes:

Ensure you have a backup of your data before executing delete operations, as they are irreversible.

Familiarize yourself with the data being targeted to avoid unintentional data loss.

Conclusion

By following these steps, you can effectively delete entries from a SELECT query result in MySQL. You’ve learned how to utilize inline views to streamline this process and ensure accuracy before executing your delete operations. Armed with this knowledge, you should feel more confident tackling similar scenarios in your MySQL work.

If you have further questions or need assistance with MySQL queries, feel free to ask in the comments below!