Introduction to the PostgreSQL jsonb_extract_path() function

Thejsonb_extract_path() function allows you to extract a JSON sub-object from a JSONB value at a specified path.

Here's the basic syntax of thejsonb_extract_path() function:

jsonb_extract_path(target jsonb, VARIADIC path_elemstext[])

In this syntax:

• target is a JSONB data from which you want to extract data.
• path_elems is a list of paths that you want to locate the elements in the JSONB data for extraction.

Note that the path is not a JSON path. The syntax for thepath_elems parameter is as follows:

• 'key': Access a specific key in the JSON object.
• 'array_index': Access an element in a JSON array using its index.

To navigate through the nested objects or array, you can chain these path components together.

Suppose you have the following JSON object:

{  "employee": {    "name":"John Doe",    "age":22,    "contacts": [      {"type":"email","value":"john.doe@example.com"},      {"type":"phone","value":"408-123-456"}    ]  }}

Here are some examples of the path expressions:

• 'employee' returns the entireemployee object.
• ['employee', 'name'] returns the name within the employee object, which is"John Doe".
• ['employee', 'contacts', '0', 'value'] returns the value in the first element of the contacts array, which isjohn.doe@example.com

PostgreSQL jsonb_extract_path() function examples

Let's take some examples of using thejsonb_extract_path() function.

Setting up a sample table

First,create a new table calleddocuments:

CREATE TABLE documents(   idSERIAL PRIMARY KEY,   data JSONB);

Second,insert two rows into thedocuments table:

INSERT INTO documents(data)VALUES  ('{"employee":{"name":"John Doe","age":22,"contacts":[{"type":"email","value":"john.doe@example.com"},{"type":"phone","value":"408-123-456"}]}}'),  ('{"employee":{"name":"Jane Doe","age":21,"contacts":[{"type":"email","value":"jane.doe@example.com"},{"type":"phone","value":"408-123-789"}]}}');

Basic jsonb_extract_path() function examples

The following example uses thejsonb_extract_path() function to extract the employee object:

SELECT  jsonb_extract_path(data,'employee') employeeFROM  documents;

Output:

employee------------------------------------------------------------------------------------------------------------------------------------------- {"age": 22, "name": "John Doe", "contacts": [{"type": "email", "value": "john.doe@example.com"}, {"type": "phone", "value": "408-123-456"}]} {"age": 21, "name": "Jane Doe", "contacts": [{"type": "email", "value": "jane.doe@example.com"}, {"type": "phone", "value": "408-123-789"}]}(2 rows)

The following example uses thejsonb_extract_path() function to extract the names of employees:

SELECT  jsonb_extract_path(data,'employee','name')nameFROM  documents;

Output:

name------------ "John Doe" "Jane Doe"(2 rows)

The following example uses thejsonb_extract_path() function to extract the emails of employees:

SELECT  jsonb_extract_path(    data,'employee','contacts','0',    'value'  ) emailFROM  documents;

Output:

email--------------------- "john.doe@example.com" "jane.doe@example.com"(2 rows)

Summary

• Use thejsonb_extract_path() function to extract JSON sub-object at the specified path.

Last updated onFebruary 24, 2024

On this page

• Introduction to the PostgreSQL jsonb_extract_path() function
• PostgreSQL jsonb_extract_path() function examples
• Summary