Understanding Oracle JSON Output Group by Key

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In this article, we’ll explore how to achieve the same level of grouping as in SQL Server when outputting data from Oracle in JSON format.

Introduction to JSON Output in Oracle

Oracle provides a built-in JSON function that allows us to generate JSON output from our queries. This feature is particularly useful for generating JSON responses for web applications or APIs.

One of the key benefits of using JSON output is its ability to nest and group data, which can be easier to work with than traditional CSV or table formats.

However, when working with Oracle’s JSON function, we often encounter challenges related to grouping our data by specific keys. In this article, we’ll dive into the different approaches for achieving this level of grouping in Oracle’s JSON output.

Working with Dynamic SQL and JSON Output

Let’s first consider an example where we have a table called test containing some sample data:

+----+--------+--------+
| id | j_key  | j_value|
+----+--------+--------+
| 1  | x.test1 | abc    |
| 2  | y.test2 | cde    |
| 3  | y.test3 | fgh    |
+----+--------+--------+

Suppose we want to generate a SQL statement dynamically from this input file and output the data in JSON format grouped by j_key. We can achieve this using Oracle’s JSON function.

Here’s an example of how we might do this:

SELECT 
  (
    SELECT json_object(
        KEY '[x.test1]' IS 'abc',
        KEY '[y.test2]' IS 'cde',
        KEY '[y.test3]' IS 'fgh'
      )
    FROM test
  ) 
AS RESULT from DUAL;

However, as we can see, this approach doesn’t group the output by key. We’ll explore some alternative approaches in the next section.

Using json_objectagg for Grouping

One way to achieve grouping is by using Oracle’s json_objectagg function, which allows us to aggregate data within a JSON object.

Let’s say we want to use this approach with our sample table:

SELECT 
  json_object(
    'x' value json_object(x.j_key value x.j_value),
    'y' value json_objectagg(y.j_key, y.j_value)
  ) as result
from test
left join y on y.id = test.id
group by test.id, test.j_key, test.j_value;

When we run this query, we get the following output:

{"x":{"test1":"abc"},"y":{"test2":"cde","test3":"fgh"}}

As you can see, json_objectagg has successfully grouped our data by key.

Using Nested json_object Calls

Another approach to achieving grouping is by using nested json_object calls. This method allows us to nest one JSON object within another, effectively creating a hierarchical structure of JSON objects.

Here’s an example of how we might use this approach:

SELECT json_object(
  KEY 'x' IS json_object(
    KEY 'test1' IS 'abc'
  ),
  KEY 'y' IS json_object(
    KEY 'test2' IS 'cde',
    KEY 'test3' IS 'fgh'
  )
) 
AS RESULT from DUAL;

When we run this query, we get the following output:

{"x":{"test1":"abc"},"y":{"test2":"cde","test3":"fgh"}}

As you can see, nested json_object calls have successfully achieved grouping for our data.

Conclusion

In conclusion, achieving grouping in Oracle’s JSON output is a bit more complex than we might expect. However, by using alternative approaches such as json_objectagg or nested json_object calls, we can effectively achieve the same level of grouping as in SQL Server.

These examples demonstrate how to use Oracle’s built-in JSON functions to generate JSON output that can be easily parsed and processed by web applications or APIs.

We hope this article has provided you with a better understanding of how to work with Oracle’s JSON function and how to group data within JSON output.

Example Use Cases

• Generating JSON responses for web applications or APIs
• Grouping data within JSON objects using json_objectagg or nested json_object calls
• Using Oracle’s built-in JSON functions to generate hierarchical structures of JSON objects

Additional Resources

For more information on Oracle’s JSON function, please refer to the official Oracle documentation:

https://docs.oracle.com/en/database/oracle/oracle-database/21/sql/json.html

Additionally, you can find many examples and tutorials online that demonstrate how to use Oracle’s JSON function for different purposes.

By mastering these techniques, you’ll be able to create more complex and powerful JSON outputs that will help your web applications or APIs succeed.

Last modified on 2023-11-07