Query for element of array in JSON column

Question

Recently upgraded to using PostgreSQL 9.3.1 to leverage the JSONfunctionalities. In my table I have a json type column that has a structure like this:

{
 "id": "123",
 "name": "foo",
 "emails":[
 {
 "id": "123",
 "address": "somethinghere"
 },
 {
 "id": "456",
 "address": "soemthing"
 }
 ]
} 

This is just dummy data for the purpose of the question.

Is it possible to query for a specific item in the emails array based on the id?
Pretty much: "return email where id=123)"?

Answer 1

For Postgres 9.4+ see adamc's later answer. Or:

• Query for array elements inside JSON type

Original answer for Postgres 9.3

Yes, that's possible:

SELECT *
FROM tbl t, json_array_elements(t.json_col->'emails') AS elem
WHERE elem->>'id' = 123;

tbl being your table name, json_col the name of the JSON column.

See also:

• How do I query using fields inside the new PostgreSQL JSON datatype?

About the implicit CROSS JOIN LATERAL:

• PostgreSQL unnest() with element number

Index to support this kind of query:

• Index for finding an element in a JSON array

• w0rp: This is the best answer I have seen for this type of question so far.
• Cepr0: @ErwinBrandstetter Sorry for off-top, but could you please help with this issue: stackoverflow.com/q/49532773 (Thanks in advance!)

Answer 2

With a JSONB column in Postgres 9.4+ you can use the contains operator @> to query for an element in an array:

SELECT * FROM jsontest WHERE data @> '{ "emails": [{ "id": "123" }] }';

See Query for array elements inside JSON type for more details.

Here is a working example:

CREATE TABLE jsontest(data JSONB NOT NULL);
INSERT INTO jsontest VALUES (
 '{
 "name": "foo",
 "id": "123",
 "emails": 
 [
 {
 "address": "somethinghere",
 "id": "123"
 },
 {
 "address": "soemthing",
 "id": "456"
 }
 ]
 }'
);
SELECT * FROM jsontest WHERE data @> '{ "emails": [{ "id": "123" }] }';
data
----
{"id": "123", "name": "foo", "emails": [{"id": "123", "address": "somethinghere"}, {"id": "456", "address": "soemthing"}]}

(1 row)

• Pranay Soni: how to delete address by id 123 ?
• adamc: delete FROM jsontest WHERE data @> '{ "emails": [{ "id": "123" }] }';

Answer 3

Came across this post and found that you can directly query on table like this:

SELECT *
FROM table_name, json_array_elements(json_column) AS data
WHERE data->>'id' = 123;

Omitting this part:

json_array_elements(t.json_col->'emails')

• Mercutionario: this is super super useful I have been struggling with CTE to try and make it work, and this just solves my need beautifully. Thanks!

Answer 4

You can do it as simple as :

SELECT * FROM table WHERE emails->>'id' = '123';

it seems you store the id as string, if it was an integer you can do it like this :

SELECT * from table WHERE cast(emails->>'id' as integer ) = 123 ;

or you can get all the rows with id> 10

SELECT * from table WHERE cast(emails->>'id' as integer ) > 10 ;

• adamc: I've tried this on Postgres 9.4.4 and it doesn't work: