How to Display null Instead of Empty JSON Object in DB2 Queries

Learn how to modify your DB2 SQL queries to show `null` instead of empty JSON objects by utilizing conditional functions effectively.
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How to Display null Instead of Empty JSON Object in DB2 Queries

When working with JSON data in DB2, it’s not uncommon to encounter scenarios where you want your SQL queries to return null values instead of empty JSON objects. This can be particularly useful for clarity in data representation and handling, especially when dealing with client applications that may interpret an empty object differently than a null value. In this post, we'll guide you through how to achieve this by modifying your SQL query.

The Problem: Returning Empty Objects

Let's take a look at the initial problem you may be facing. In your DB2 database, you want your query to return a result set that looks like this:

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

However, the default output may instead yield empty JSON objects, such as {}. This can lead to confusion and complications in handling the results.

Example of the Default Query

Here’s an example of a query that might produce an empty JSON object when you expect a null value:

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

When executed, this query may return a result set that includes empty objects instead of null values when no data exists for the specified fields.

The Solution: Modifying the Query

To change the output from empty JSON objects to null, we can utilize the NULLIF function in our SQL query. The NULLIF function returns null if the two arguments are equal; otherwise, it returns the first argument.

Updated SQL Query

Here’s how to update your SQL query accordingly:

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

Breakdown of the Query

Using NULLIF:

The NULLIF function checks the result of JSON_OBJECT(...) and compares it to an empty string ('{}'). If the result is indeed an empty JSON object, NULLIF will return null for that entry.

JSON_OBJECT Construction:

The JSON_OBJECT function constructs a JSON object from the provided fields (NAME and SIZE). The ABSENT ON NULL clause ensures that any fields that are NULL are not included in the final JSON object output.

Values Clause:

For demonstration purposes, values are provided directly within the query utilizing a derived table syntax, which allows us to simulate a small dataset.

Sample Output

When you run the modified query, you'll receive results structured like this:

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

As you can see, instead of returning an empty object for the third identifier, the output is now null as desired.

Conclusion

In summary, if you want your DB2 SQL queries to show null instead of empty JSON objects, simply implement the NULLIF function in conjunction with JSON_OBJECT. This approach not only clarifies the output but also maintains consistency in how absent data is represented in your application logic.

By following the steps outlined in this guide, you can confidently handle empty JSON outputs and convey more accurate data representations in your database queries.

Feel free to test this approach in your queries and refine your data handling process in DB2!