SQL Server JSON Support

Storing JSON Data in SQL Server

SQL Server does not have a dedicated JSON data type. Instead, JSON data is stored as NVARCHAR columns.

You can store JSON documents as text in columns defined as NVARCHAR(MAX) or NVARCHAR with a specific length.

• Use NVARCHAR(MAX) for large JSON documents.
• Validate JSON format before storing to avoid errors during querying.
• Consider constraints or triggers to enforce JSON validity.

Querying JSON Data

SQL Server provides several built-in functions to extract and query JSON data stored in string columns.

These functions allow you to retrieve scalar values, JSON objects, or arrays from JSON text.

• JSON_VALUE: Extracts a scalar value from a JSON string.
• JSON_QUERY: Extracts an object or array from JSON text.
• OPENJSON: Parses JSON text and returns a tabular result set.

Modifying JSON Data

SQL Server provides the JSON_MODIFY function to update values within a JSON string.

This function returns a new JSON string with the specified modifications applied.

• Use JSON_MODIFY to update, add, or remove properties in JSON text.
• Always assign the result of JSON_MODIFY back to the column to persist changes.

Best Practices for JSON in SQL Server

While JSON support is powerful, following best practices ensures good performance and maintainability.

• Validate JSON data before inserting or updating.
• Use appropriate NVARCHAR sizes to balance storage and performance.
• Create computed columns with JSON_VALUE for indexing frequently queried JSON properties.
• Avoid storing excessively large JSON documents in a single column.
• Use OPENJSON with CROSS APPLY for efficient querying of JSON arrays.