![]() The json_agg function is useful for creating JSON arrays from query results, which can be particularly handy when working with JSON data in PostgreSQL. The GROUP BY clause groups the results by department.We selected the department and used json_agg(name) to aggregate the names of employees in the “HR” department into a JSON array.Then on your Postgres server: CREATE EXTENSION IF NOT EXISTS plpythonu CREATE LANGUAGE plpythonu CREATE OR REPLACE FUNCTION prettyprintjson (data text) RETURNS json AS import json return json.dumps (json.loads (data), indent4) LANGUAGE plpythonu Share. The result of this query will be: | department | employees | |-|-| | HR | | On the server install: sudo apt-get install postgresql-plpython-9.4. You can use the json_agg function to aggregate the names of employees in the “HR” department into a JSON array: SELECT department, json_agg(name) AS employees FROM employees WHERE department = 'HR' GROUP BY department Here's a very simple one that returns the length of a string: CREATE OR REPLACE FUNCTION slength(s text) RETURNS int AS BEGIN RETURN length(s) END LANGUAGE plpgsql It's not a very useful function because length already exists but the point is to see a basic custom function. Here’s an example of how to use the json_agg function to aggregate values from a table:Ĭonsider a table named employees: CREATE TABLE employees ( id serial PRIMARY KEY, name text, department text ) Īnd it contains the following data: | id | name | department | |-|-|-| | 1 | Alice | HR | | 2 | Bob | IT | | 3 | Carol | HR | | 4 | David | IT | Where expression is the value or column you want to aggregate into the JSON array. I have a PostgreSQL function which successfully returns its data as. I've managed to write the function BUT it only returns the first row. I currently have the query hard coded in a node.js implementation but would like to move it into the Db and simply call a function. Here is the basic syntax for the json_agg function: json_agg(expression) I have a query which by itself produces several rows of data and I use the rowtojson function to format that data for use in a rest api. ![]() This function is particularly useful when you want to combine rows or values into a single JSON array in the result of a query. It takes one or more values and returns a JSON array that contains those values as elements. The json_agg function is used to aggregate values into a JSON array in PostgreSQL database. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |