Returning values from an array of JSONB objects.

On 4/13/16, sighup <rts@sighup.eu> wrote:

Hi, please excuse either my stupidity or naivety regarding this but I'm
a bit confused. Give the following basic table structure :

TABLE Data (
ID INT NOT NULL,
Markers jsonb NOT NULL
);

And the following data:

INSERT INTO Data (ID, Markers) VALUES(1, '[ {"idle": true, "items": 8,
"done": 0}, {"idle": true, "items": 8, "done": 0}]') ;

How can I extract the value of the 'items' key either as two rows and or
a sum of both.

You should use a proper function "jsonb_populate_recordset" [1]http://www.postgresql.org/docs/9.5/static/functions-json.html -- Best regards, Vitaly Burovoy.

I had thought that :

SELECT Markers->'items' AS Items FROM Data WHERE (ID = X) ;

would have done the job but all I get is an empty column,

If course you get empty result because the operator "->" is "Get JSON
array *element*".

of course using :

SELECT Markers->0->'items' AS Items FROM Data WHERE (ID = X) ;

Produces a single row but isn't exactly what I want.I have of course
searched but not found a definitive answer, or maybe that should read
'one I can understand'.

I'm using PostgreSQL 9.5 on Linux with pgAdmin III on Mac.

--
Bill

[1]: http://www.postgresql.org/docs/9.5/static/functions-json.html -- Best regards, Vitaly Burovoy
--
Best regards,
Vitaly Burovoy

--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

On 4/13/16, Vitaly Burovoy <vitaly.burovoy@gmail.com> wrote:

On 4/13/16, sighup <rts@sighup.eu> wrote:

Hi, please excuse either my stupidity or naivety regarding this but I'm
a bit confused. Give the following basic table structure :

TABLE Data (
ID INT NOT NULL,
Markers jsonb NOT NULL
);

And the following data:

INSERT INTO Data (ID, Markers) VALUES(1, '[ {"idle": true, "items": 8,
"done": 0}, {"idle": true, "items": 8, "done": 0}]') ;

Prerequisite:
CREATE TYPE myrowtype AS (idle bool, items int, done int);

Couple examples:

How can I extract the value of the 'items' key either as two rows

SELECT (jsonb_populate_recordset(NULL::myrowtype, Markers)).items
FROM Data WHERE (ID = X);

and or a sum of both.

SELECT sum(items) FROM(
SELECT (jsonb_populate_recordset(NULL::myrowtype, Markers)).items
FROM Data WHERE (ID = X)
)AS t;

You should use a proper function "jsonb_populate_recordset" [1].

[1] http://www.postgresql.org/docs/9.5/static/functions-json.html

--
Best regards,
Vitaly Burovoy

--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

On 13/04/2016 11:53, Vitaly Burovoy wrote:

On 4/13/16, Vitaly Burovoy <vitaly.burovoy@gmail.com> wrote:

On 4/13/16, sighup <rts@sighup.eu> wrote:

Hi, please excuse either my stupidity or naivety regarding this but I'm
a bit confused. Give the following basic table structure :

TABLE Data (
ID INT NOT NULL,
Markers jsonb NOT NULL
);

And the following data:

INSERT INTO Data (ID, Markers) VALUES(1, '[ {"idle": true, "items": 8,
"done": 0}, {"idle": true, "items": 8, "done": 0}]') ;

Prerequisite:
CREATE TYPE myrowtype AS (idle bool, items int, done int);

Couple examples:

How can I extract the value of the 'items' key either as two rows

SELECT (jsonb_populate_recordset(NULL::myrowtype, Markers)).items
FROM Data WHERE (ID = X);

and or a sum of both.

SELECT sum(items) FROM(
SELECT (jsonb_populate_recordset(NULL::myrowtype, Markers)).items
FROM Data WHERE (ID = X)
)AS t;

You should use a proper function "jsonb_populate_recordset" [1].

[1] http://www.postgresql.org/docs/9.5/static/functions-json.html

Hello Vitaly,

I have just tried this and of course it works, thank you ever so much
for your time and effort I genuinely appreciate it.

--
Bill

--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

## sighup (rts@sighup.eu):

How can I extract the value of the 'items' key either as two rows and or
a sum of both.

select id, jsonb_array_elements(markers)->>'items' from data;
And as jsonb_array_elements() returns a setof jsonb:
with tab(id, items) as (
select id, (jsonb_array_elements(markers)->>'items')::integer from d
) select id, sum(items) from tab group by id;

Regards,
Christoph

--
Spare Space

--
Sent via pgsql-general mailing list (pgsql-general@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general