JSON Functions

Modern applications often deal with flexible, nested, and semi-structured data. From user preferences to API responses, the JSON format has become a go-to standard for handling such cases. Thankfully, PostgreSQL offers first-class support for JSON, allowing you to store, query, and transform JSON data directly in your database.

In this overview, we’ll explore what PostgreSQL JSON functions are, why they’re useful, and how they’re applied in real-world projects.

What Are JSON Functions in PostgreSQL?

PostgreSQL supports two types for storing JSON data: JSON and JSONB. While JSON stores the data as text, JSONB stores it in a binary format that’s more efficient for indexing and querying.

To work with this data, PostgreSQL provides a wide set of JSON functions and operators. These allow you to extract values, search within JSON documents, transform structures, and even build JSON objects on the fly.

Whether you're reading nested keys or filtering results based on dynamic fields, these functions give you full control over JSON content inside your SQL queries.

Why Are JSON Functions Useful?

In many cases, relational tables with fixed columns aren’t flexible enough. JSON allows you to store complex and variable data structures—without needing to redesign your schema each time.

PostgreSQL’s JSON functions are useful because they let you:

• Handle unstructured or partially structured data

• Query deeply nested values without splitting data into multiple tables

• Store user-specific settings, logs, or dynamic metadata

• Build flexible APIs directly from your database

• Avoid over-normalizing data that doesn’t fit a strict relational model

And since PostgreSQL integrates JSON support into its SQL engine, you don’t need to move data into other tools to parse or analyze it.

Real-World Use Cases

PostgreSQL JSON functions are especially valuable in:

• Web and mobile applications, where user preferences or app settings vary

• Logging systems, where different events may contain different fields

• APIs, where data is received or served in JSON format

• Data lakes or ETL processes, where incoming data structures are not yet standardized

• Product catalogs, where items may have different sets of attributes

This flexibility allows teams to move faster without sacrificing structure or performance.

What Will You Learn in This Section?

In this part of the documentation, we cover the most important JSON functions and operators available in PostgreSQL. Topics include:

• Choosing between JSON and JSONB

• Using access operators like ->, ->>, #>, and #>> to extract values

• Working with functions like jsonb_array_elements() and jsonb_each() to unpack nested arrays or objects

• Querying and filtering JSON data using conditions

• Creating and aggregating JSON with functions like json_build_object() or json_agg()

• Indexing strategies for JSON columns, especially with GIN indexes

Each function will be introduced with examples and best practices, helping you understand both how and when to use them.