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How do you convert a JSON array stored in a column into a relational table format that can be queried like normal rows? How do you generate JSON formatted output directly from a SQL query's result set? How do you update a specific value within a JSON document stored in a column without replacing the entire JSON text? How would you validate that a value stored in a column actually contains well formed JSON before allowing it to be inserted or updated?
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SQL Server › JSON Support in SQL Server

What are the performance considerations and limitations of querying JSON data stored as text compared to using normalized relational columns?

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Answer

Since JSON is stored as plain text, SQL Server must parse it every time a JSON function is used, which is generally slower than querying a properly indexed relational column, and while you can create a computed column based on a JSON_VALUE expression and then index that computed column, this only helps for specific, frequently queried JSON properties rather than the entire document.
ALTER TABLE Orders ADD CustomerEmail AS JSON_VALUE(OrderData, '$.email');
CREATE INDEX IX_Orders_Email ON Orders(CustomerEmail);
Real-world example A team notices queries filtering on a customer email stored inside a JSON column are slow, so they create a computed column extracting just that email value and index it, significantly speeding up that specific type of query.

Common follow-ups: When does it make more sense to fully normalize data instead of storing it as JSON?;How much overhead does parsing JSON add compared to querying a normal column directly?

Data Types & Schema Design;Indexes
All 7 JSON Support in SQL Server questions