Скачать или смотреть Resolving MySQL Query Issues with JOIN to Update Two Tables

Learn how to effectively utilize `JOIN` in MySQL to update multiple tables and avoid common errors when referencing column names.
---
This video is based on the question https://stackoverflow.com/q/76251537/ asked by the user 'GurusGuru' ( https://stackoverflow.com/u/11349567/ ) and on the answer https://stackoverflow.com/a/76251789/ provided by the user 'michal.jakubeczy' ( https://stackoverflow.com/u/2470765/ ) 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: Mysql query based on 2 tables

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.
---
Resolving MySQL Query Issues with JOIN to Update Two Tables

When working with MySQL databases, it’s not uncommon to run into problems while trying to run queries that involve multiple tables. A common scenario is trying to update data in one table based on conditions defined in another. In this post, we'll tackle a specific issue involving two tables: new_test2 and keywordssector. If you’ve encountered an error when attempting to join these tables in a query, keep reading for a clear solution!

The Problem

You have two MySQL tables:

new_test2: This table includes fields like title, noticeText, and sectoradd.

keywordssector: This table contains fields for keywords and sector.

The goal is to search for keywords in the fields of new_test2 and add relevant sector codes from the keywordssector table to the sectoradd column in new_test2. However, you’re running into an error:

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

This error is likely occurring because you are referencing a column from the keywordssector table without properly joining it to the new_test2 table in your query.

Understanding the Cause

The error message indicates that MySQL cannot recognize the reference to keywordssector.keywords because it is not included in the FROM clause of your query. Without a JOIN, MySQL doesn’t know how to connect the two tables for the operations you wish to perform.

The Solution

To address this issue, you need to properly format your SQL query with a JOIN. Here's the revised version of your update query:

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

Breaking It Down

JOIN Clause:

We are joining new_test2 with keywordssector based on a condition that checks if the title or noticeText contains any of the keywords.

SET Clause:

This part of the query updates the sectoradd column by appending the sector value from keywordssector if it is not already present.

WHERE Clause:

We ensure that the operation takes place only for non-null sector values and avoids duplicating sectors already listed in sectoradd.

Conclusion

By rewriting your SQL query to include the necessary JOIN, you can effectively update your tables based on the multiple conditions set forth. This approach eliminates the errors and allows for seamless data management across related tables.

If you encounter further issues or have specific questions about variations, feel free to reach out!