Issues creating Json object on snowflake using Sql - sql

Question

I am new to Snowflake and I am trying to create a new table from an existing table and converting some rows into json format.
what I have on snowflake (table name: lex)
area
source
type
date
One
modak
good
2021
what I want to achieve on snowflake
area
sources
One
[{"source": "modak","period": {"type": "good","date": "2021"} }]
Any direction on how to go about it using SQl will be appreciated.

Answer 1

You can use object_construct to produce JSON objects:
select
area, array_construct( object_construct( 'source', source, 'period', object_construct( 'type',type, 'date',date )) ) sources
from
values ('One','modak','good','2021') tmp (area, source,type,date);
+------+-------------------------------------------------------------------------+
| AREA | SOURCES |
+------+-------------------------------------------------------------------------+
| One | [ { "period": { "date": "2021", "type": "good" }, "source": "modak" } ] |
+------+-------------------------------------------------------------------------+
I also used array_construct to add the brackets ([])
OBJECT_CONSTRUCT:
https://docs.snowflake.com/en/sql-reference/functions/object_construct.html
ARRAY_CONSTRUCT:
https://docs.snowflake.com/en/sql-reference/functions/array_construct.html
PS: Order of the JSON elements are not important when accessing them:
select parse_json(j):source, parse_json(j):period.type
from
values
('{ "period": { "date": "2021", "type": "good" }, "source": "modak" }'),
('{"source": "modak","period": {"type": "good","date": "2021"} }') tmp(j);
+----------------------+---------------------------+
| PARSE_JSON(J):SOURCE | PARSE_JSON(J):PERIOD.TYPE |
+----------------------+---------------------------+
| "modak" | "good" |
| "modak" | "good" |
+----------------------+---------------------------+

Answer 2

So the complete answer is:
WITH lex AS (
SELECT * FROM VALUES
('One', 'modak', 'good', 2021)
v(area, source, type, date)
)
SELECT l.area,
ARRAY_AGG(OBJECT_CONSTRUCT('source', l.source, 'period', OBJECT_CONSTRUCT('type', l.type, 'date', l.date))) as sources
FROM lex AS l
GROUP BY 1
ORDER BY 1;
which gives:
AREA
SOURCES
One
[ { "period": { "date": 2021, "type": "good" }, "source": "modak" } ]
Gokhan's answer show how to build a static array with ARRAY_CONSTRUCT, but if you have a dynamic input like:
WITH lex AS (
SELECT * FROM VALUES
('One', 'modak', 'good', 2021),
('One', 'modak', 'bad', 2022),
('Two', 'modak', 'good', 2021)
v(area, source, type, date)
)
And you want, the below, you will need to use ARRAY_AGG
AREA
SOURCES
One
[ { "period": { "date": 2021, "type": "good" }, "source": "modak" }, { "period": { "date": 2022, "type": "bad" }, "source": "modak" } ]
Two
[ { "period": { "date": 2021, "type": "good" }, "source": "modak" } ]