Скачать или смотреть Combining Two JSON Objects into a Single JSON Object in PostgreSQL 15

Learn how to effectively combine two JSON objects in `PostgreSQL 15`, tackling common challenges and providing clear steps to achieve your desired JSON structure.
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How to Combine Two JSON Objects into a Single JSON Object in PostgreSQL 15

In today’s data-driven world, using JSON (JavaScript Object Notation) in databases has become increasingly important. With PostgreSQL 15, you might encounter situations where you need to combine multiple JSON objects into a single JSON object. This can be particularly useful when you want to aggregate data from different tables within your database. In this guide, we will explore how to combine two JSON objects into a single JSON object in PostgreSQL 15 efficiently.

The Problem Statement

Consider a common scenario where you have a category and its associated products in separate tables. When you query these tables separately, you might produce JSON outputs like this:

Category JSON Output:

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

Products JSON Output:

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

However, your goal is to merge these two JSON outputs into a single JSON object, structured as follows:

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

A Step-by-Step Solution

To achieve this desired output, you need to leverage PostgreSQL’s powerful JSON functions properly. Here’s a breakdown of the solution, step by step:

Step 1: Utilize the JOIN Clause

You need to perform a SQL JOIN that links the category table and product table based on their relationship. In this case, we can use an INNER JOIN on category_id:

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

Step 2: Constructing the Query

Now, let's put everything together in a single query. You will use the to_json() function to convert the category data as JSON, while using json_agg() to aggregate all products related to that specific category.

Here’s the full SQL query you should use:

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

Explanation of the Query

to_json(c.*)::jsonb: This function converts all columns of the category into a JSONB object.

json_build_object('products', json_agg(p.*))::jsonb: This creates a new JSON object with a key named products that contains all aggregated product information as nested JSON.

|| operator: The || operator merges two JSONB objects into one.

GROUP BY c.id: This clause groups the results based on the unique identity of the category, ensuring that you do not get duplicate rows.

Conclusion

By following these steps, you can effectively combine two JSON objects into a single JSON object in PostgreSQL 15. This technique not only improves the readability of your data but also enhances the way you manage and retrieve complex data structures in your applications. If you have any questions or would like to share your experiences, feel free to leave a comment below!