select json_object() into list postgres function

Question

Here i am trying to get all the select values in a varible.

 DECLARE
 ite json;
 BEGIN 
 select INTO ite from json_object('{1}','{1}'); 
 RETURN ite;

when i call this function i got the result null.

Answer 1

Have a look at SELECT INTO in Postgres docs.

SELECT INTO: define a new table from the results of a query

Synopsis

[ WITH [ RECURSIVE ] with_query [, ...] ]
SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ]
 * | expression [ [ AS ] output_name ] [, ...]
 INTO [ TEMPORARY | TEMP | UNLOGGED ] [ TABLE ] new_table
 [ FROM from_item [, ...] ]
 [ WHERE condition ]
 [ GROUP BY expression [, ...] ]
 [ HAVING condition [, ...] ]
 [ WINDOW window_name AS ( window_definition ) [, ...] ]
 [ { UNION | INTERSECT | EXCEPT } [ ALL | DISTINCT ] select ]
 [ ORDER BY expression [ ASC | DESC | USING operator ] [ NULLS { FIRST | LAST } ] [, ...] ]
 [ LIMIT { count | ALL } ]
 [ OFFSET start [ ROW | ROWS ] ]
 [ FETCH { FIRST | NEXT } [ count ] { ROW | ROWS } ONLY ]
 [ FOR { UPDATE | SHARE } [ OF table_name [, ...] ] [ NOWAIT ] [...] ]

Examples

Create a new table films_recent consisting of only recent entries from the table films:

SELECT * INTO films_recent FROM films WHERE date_prod >= '2002-01-01';

---

Try the next syntax:

CREATE OR REPLACE FUNCTION fn_get_json()
RETURNS text AS
$$
DECLARE
 ite text;
BEGIN 
 select * into ite from json_object('{1}','{1}');
 return ite;
END
$$
LANGUAGE plpgsql;

select * from fn_get_json();

| fn_get_json |
| :---------- |
| {"1" : "1"} |

db<>fiddle here

Or as pointed out in comments a reduced version:

CREATE OR REPLACE FUNCTION fn_get_json()
RETURNS json AS
$$
BEGIN 
 return json_object('{1}','{1}');
END
$$
LANGUAGE plpgsql;

Or even simpler with a SQL function:

CREATE OR REPLACE FUNCTION fn_get_json()
RETURNS json AS
$$
 select json_object('{1}','{1}');
$$
LANGUAGE sql;

Answer 2

select values in a varible

I think what you want here is a jsonb_agg which aggregates values as a JSON array.

SELECT jsonb_agg(foo)
FROM ( VALUES (1,2,'foo'), (2,3,'bar') ) AS foo(a,b,c);
 jsonb_agg 
--------------------------------------------------------------
 [{"a": 1, "b": 2, "c": "foo"}, {"a": 2, "b": 3, "c": "bar"}]

There is also jsonb_object_agg(name, value)

SELECT jsonb_object_agg(a,b)
FROM ( VALUES ('key1','value1'),('key2','value2') ) AS t(a,b);
 jsonb_object_agg 
--------------------------------------
 {"key1": "value1", "key2": "value2"}

Though I admit it's somewhat hard to tell you've provided so little.