Скачать или смотреть Optimizing INSERT Statements with Subqueries in MySQL

Learn how to efficiently insert records in MySQL using data from the same table with optimized subqueries. This guide discusses the benefits of using JOINs over subqueries for better performance.
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This video is based on the question https://stackoverflow.com/q/73845389/ asked by the user 'williamohara' ( https://stackoverflow.com/u/14249625/ ) and on the answer https://stackoverflow.com/a/73847169/ provided by the user 'Akina' ( https://stackoverflow.com/u/10138734/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Optimizing INSERT Statements with Subqueries in MySQL

When working with databases, efficiency is key, especially when it comes to inserting new records. A common scenario is needing to insert a new record using data from another record within the same table. In this post, we will address a specific question: How can we effectively insert a new tenant with the same domain name as its parent?

The Challenge at Hand

Imagine you're managing a multi-tenant application, and you have a situation where a new tenant needs to inherit the secondary_domain from an existing tenant identified by the UUID 0904ba44-9d41-418a-bbd8-2c70506c3432. The main queries we have in this situation are as follows:

Existing Solutions

Using a Subquery:

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

Using a JOIN:

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

The Recommendation: A More Optimized Approach

While both methods are functional, there’s a more efficient way to perform this operation. The ideal approach eliminates redundancy and leverages the benefits of direct selection from the table rather than using nested subqueries. Here’s the suggested query:

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

Why This Query is More Efficient

1. Reduced Complexity:
The suggested method eliminates unnecessary subqueries, leading to a simpler and more readable SQL statement.

2. Performance Improvements:
By directly selecting from the table instead of nesting multiple subqueries, you minimize processing time. Here's a breakdown of the performance metrics you can expect with the optimized query:

Less overhead resulting from reduced logical reads.

Improved execution plan which reduces the number of table scans.

3. Scalability:
As your dataset grows, this method is likely to scale better than the nested approaches, ensuring that your application remains responsive to insertion requests.

Understanding MySQL Query Plans

To further understand the efficiency of the presented solutions, it's beneficial to analyze the execution plan using the EXPLAIN statement. When you run EXPLAIN on each of the queries, you can observe how MySQL interprets the operations, including:

Type of join (e.g., ALL, ref, etc.)

The number of rows identified or affected

The indexes being used, if any

Conclusion

Choosing the right method for inserting records can significantly impact the performance of your application. In cases where you need to replicate existing data, utilizing simplified queries that directly draw from the same table using SELECT can yield better results than convoluted subqueries. By applying these concepts, you can enhance your MySQL optimization skills and ensure your database interactions are both efficient and scalable.

So, the next time you're faced with a similar situation, remember to consider the streamlined approach that directly sources data from the existing records!