Oracle JSON_TABLE: Transforming JSON into Relational Format
Tags: oracle, sql, database
Published: 2023-06-20 13:15:22

The function **JSON\_TABLE** allows us to transform JSON data into a relational format.

This article will explore the Oracle JSON\_TABLE function and its syntax and provide examples to demonstrate its usage and capabilities.

## Table of Contents

- [Understanding Oracle JSON\_TABLE](#understanding-oracle-jsontable)
- [Example Using Oracle JSON\_TABLE](#example-using-oracle-jsontable)
- [Additional Considerations](#additional-considerations)
- [Conclusion](#conclusion)

## Understanding Oracle JSON\_TABLE

The JSON\_TABLE function in Oracle converts JSON data into a relational format by extracting specified JSON data elements and returning them as rows and columns.

It enables you to query and process JSON data using SQL techniques, making integrating JSON and relational data easier.

The Syntax of Oracle JSON\_TABLE:

```sql
JSON_TABLE(
	json_data
    , path_expression COLUMNS (column_name data_type PATH json_path_exp) [, ...])

```

- `json_data`: The JSON document or column from which to extract data.
- `path_expression`: The JSON path expression specifies the elements to extract.
- `column_name`: The name to assign to the extracted JSON element.
- `data_type`: The data type of the extracted JSON element.
- `json_path_exp`: The JSON path expression to access the specific element within the JSON structure.

## Example Using Oracle JSON\_TABLE

Let's consider a practical example to illustrate the usage of Oracle **JSON\_TABLE**. Suppose we have a JSON document representing a list of employees and their details:

```sql
{
  "employees": [
    { "name": "John Doe", "age": 30, "position": "Software Engineer" },
    { "name": "Jane Smith", "age": 35, "position": "Project Manager" } 
  ]
}
```


We can use JSON\_TABLE to extract the employee details and transform them into a relational format:

```sql
SELECT A.NAME, A.AGE, A.POSITION
FROM JSON_TABLE(
    JSON_VALUE
    , '$.employees[*]' COLUMNS (
        NAME VARCHAR PATH '$.name',
        AGE NUMBER PATH '$.age',
        POSITION VARCHAR PATH '$.position'
    )
) A
```

### Usage of JSON_TABLE

In the above example, we use the JSON\_TABLE function to extract the "name," "age," and "position" elements from the "employees" array.

Using the COLUMNS clause, we assign them to corresponding columns with appropriate data types.

The resulting query retrieves the employee details in a relational format.

## Additional Considerations

- The JSON\_TABLE function supports advanced features such as nested JSON structures, array handling, and object flattening.
- You can use SQL functions and expressions within the JSON\_TABLE statement to perform calculations or transformations on extracted data.
- JSON\_TABLE also supports error handling and handling missing or optional JSON elements.

## Conclusion

Oracle *JSON_TABLE* is a powerful function that enables the transformation of JSON data into a relational format.

By extracting specified JSON elements and returning them as rows and columns, JSON\_TABLE allows you to integrate JSON and relational data seamlessly.

Understanding the syntax and usage of Oracle JSON\_TABLE empowers developers to efficiently query and process JSON data within an Oracle database environment.