How to convert a table row to JSON in PostgreSQL®?

- 2 minutes read - 356 words

PostgreSQL® offers two types of data types to handle JSON data, JSON and JSONB, you can use the function to_json (to_jsonb for JSONB) to convert a table row to a JSON object.

NOTE: To review the differences between JSON and JSONB check out the related article.

NOTE: more info is available in the PostgreSQL JSON functions documentation page

 

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The dataset

The dataset is the following:

{
    "id": 778,
    "shop": "Luigis Pizza",
    "name": "Edward Olson",
    "phoneNumbers":
        ["(935)503-3765x4154","(935)12345"],
    "address": "Unit 9398 Box 2056\nDPO AP 24022",
    "image": null,
    "pizzas": [
        {
            "pizzaName": "Salami",
            "additionalToppings": ["🥓", "🌶️"]
        },
        {
            "pizzaName": "Margherita",
            "additionalToppings": ["🍌", "🌶️", "🍍"]
        }
    ]
}
Check out the description of the fields The following examples use a pizza order dataset with an order having:
  • id: 778
  • shop: “Luigis Pizza”
  • name: “Edward Olson”
  • phoneNumbers:["(935)503-3765x4154","(935)12345"]
  • address: “Unit 9398 Box 2056\nDPO AP 24022”
  • image: null
  • and two pizzas contained in the pizzas item:
[
    {
        "pizzaName": "Salami",
        "additionalToppings": ["🥓", "🌶️"]
    },
    {
        "pizzaName": "Margherita",
        "additionalToppings": ["🍌", "🌶️", "🍍"]
    }
]
If you want to reproduce the examples, check how to recreate the dataset

It can be recreated with the following script:

create table test(id serial, json_data jsonb);

insert into test(json_data) values (
'{
    "id": 778,
    "shop": "Luigis Pizza",
    "name": "Edward Olson",
    "phoneNumbers":
        ["(935)503-3765x4154","(935)12345"],
    "address": "Unit 9398 Box 2056\nDPO AP 24022",
    "image": null,
    "pizzas": [
        {
            "pizzaName": "Salami",
            "additionalToppings": ["🥓", "🌶️"]
        },
        {
            "pizzaName": "Margherita",
            "additionalToppings": ["🍌", "🌶️", "🍍"]
        }
    ]
}');

Convert a table row to JSON in PostgreSQL with the to_json function

To convert a table row to json, use the to_json function (to_jsonb to create the JSONB equivalent)

select 
    to_jsonb(
      row(33, 
         'the pizza is in the oven'::text,
         ARRAY[11,22,33,44,55])) as res_json;

Result

                                 res_json
--------------------------------------------------------------------------
 {"f1": 33, "f2": "the pizza is in the oven", "f3": [11, 22, 33, 44, 55]}
(1 row)

Review all the JSON PostgreSQL use-cases listed in the main page