What Is JSON Data Type in SQL?


Scott Campbell

In SQL, the JSON data type is a powerful feature that allows you to store and manipulate structured data in a flexible and efficient manner. JSON stands for JavaScript Object Notation, and it has become a popular format for exchanging data between different systems due to its simplicity and compatibility with various programming languages.

What is JSON?

JSON is a lightweight data interchange format that is easy for humans to read and write, as well as for machines to parse and generate. It represents data as nested key-value pairs, similar to how objects are represented in JavaScript. Here’s an example of a simple JSON object:

  "name": "John Doe",
  "age": 30,
  "city": "New York"

JSON Data Type

In SQL, the JSON data type provides a way to store JSON documents directly in the database. It allows you to efficiently query and manipulate JSON data using SQL functions and operators, making it easier to work with structured data without sacrificing performance.

Creating Columns with the JSON Data Type

To create a column with the JSON data type, you can use the JSON keyword in your table definition. For example:

CREATE TABLE employees (
  info JSON

In this example, we have created a table called employees with two columns: id, which is an integer primary key, and info, which has the JSON data type.

Storing JSON Data

To store JSON data in a column with the JSON data type, you can simply insert or update rows with valid JSON documents. For example:

INSERT INTO employees (id, info)
VALUES (1, '{"name": "John Doe", "age": 30, "city": "New York"}');

Querying JSON Data

Once you have stored JSON data in a column, you can query it using SQL operators and functions. For example, you can use the -> operator to extract a specific value from a JSON object:

SELECT info->'name' AS name,
       info->'age' AS age
FROM employees
WHERE id = 1;

This query selects the name and age values from the info column for the employee with an ID of 1.

Nested JSON Data

The JSON data type also supports nested structures, allowing you to represent more complex data hierarchies. For example:

  "name": "John Doe",
  "age": 30,
  "address": {
    "street": "123 Main St",
    "city": "New York",
    "state": "NY"

You can access nested values using a combination of the -> operator and dot notation. For example:

SELECT info->'address'->>'street' AS street,
       info->'address'->>'city' AS city
FROM employees
WHERE id = 1;

This query selects the street and city values from the nested address object for the employee with an ID of 1.

In Conclusion

The JSON data type in SQL provides a convenient way to store, query, and manipulate structured data. It allows you to work with JSON documents directly in the database, making it easier to integrate with other systems and perform complex operations. Whether you’re building a web application or working with large datasets, the JSON data type can be a valuable tool in your SQL toolkit.

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