Summary: in this tutorial, you will learn how to use the PostgreSQL jsonb_each_text() function to expand a JSON object into a set of key/value pairs of type text.

Introduction to the PostgreSQL jsonb_each_text() function

The jsonb_each_text() function allows you to expand a top-level JSON object into a set of key/value pairs. Both keys and values are text strings.

The following shows the basic syntax of the jsonb_each_text() function:

jsonb_each_text(json_object)

In this syntax:

  • json_object is the JSON object that you want to expand the key/value pairs.

The function returns a set of records where each record consists of two fields key and value, both have the type text.

If the json_object is null, the function returns an empty set. in case the json_object is not a JSON object, the function will issue an error.

PostgreSQL jsonb_each_text() function examples

Let’s take some examples of using the jsonb_each_text() function.

1) Basic PostgreSQL jsonb_each_text() function example

The following example uses the jsonb_each_text function to expand the key/value pair of a JSON object:

SELECT
  *
FROM
  jsonb_each_text(
    '{"name": "Jane", "age": 22, "city": "San Francisco"}'
  );

Output:

key  |     value
------+---------------
 age  | 22
 city | San Francisco
 name | Jane
(3 rows)

Notice that all values in the value column are text strings including the value 22.

To retrieve a particular key/value pair, you can filter keys in the WHERE clause. For example, the following statement returns the name and city of the object:

SELECT
  *
FROM
  jsonb_each_text(
    '{"name": "Jane", "age": 22, "city": "San Francisco"}'
  )
WHERE key IN ('name','city');

Output:

key  |     value
------+---------------
 city | San Francisco
 name | Jane
(2 rows)

2) Using the jsonb_each_text() function with table data

First, create a new table called links:

CREATE TABLE links (
    id SERIAL PRIMARY KEY,
    href TEXT NOT NULL,
    attributes JSONB
);

In the links table, the attributes column has the type of JSONB that stores various attributes of a link.

Second, insert some rows into the links table:

INSERT INTO links (href, attributes)
VALUES
    ('https://example.com', '{"rel": "stylesheet", "type": "text/css", "media": "screen"}'),
    ('https://example.org', '{"rel": "icon", "type": "image/x-icon"}'),
    ('https://example.net', '{"rel": "alternate", "type": "application/rss+xml", "title": "RSS Feed"}');

Third, expand the key/value pairs of the objects in attributes column into a set of key/value pairs using the jsonb_each_text() function:

SELECT
  href,
  key,
  value
FROM
  links,
  jsonb_each_text(attributes);

Output:

href         |  key  |        value
---------------------+-------+---------------------
 https://example.com | rel   | stylesheet
 https://example.com | type  | text/css
 https://example.com | media | screen
 https://example.org | rel   | icon
 https://example.org | type  | image/x-icon
 https://example.net | rel   | alternate
 https://example.net | type  | application/rss+xml
 https://example.net | title | RSS Feed
(8 rows)

Summary

  • Use the jsonb_each_text() function to expand a JSON object into a set of key/value pairs of type text.