Let's say we have this json in our database table. I want to select value from tags. I already know how to get an array from this data but I don't know how to access array members. The question would be how do I get the first value from the array? Is there a function for this task?
{
"info": {
"type": 1,
"address": {
"town": "Bristol",
"county": "Avon",
"country": "England"
},
"tags": ["Sport", "Water polo"]
},
"type": "Basic"
}
Query I already have:
SELECT JSON_QUERY(MyTable.Data, '$.info.tags')
FROM MyTable
This returns me:
["Sport", "Water polo"]
How do I get
Sport
JSON_QUERY returns an object or array. You need JSON_VALUE to return a scalar value, eg :
SELECT JSON_VALUE(Data, '$.info.tags[0]')
from MyTable
Check the section Compare JSON_VALUE and JSON_QUERY in the docs for more examples
Related
I have a table on AWS RDS PostgreSQL that stores JSON objects. For instance I have this registry:
{
"id": "87b05c62-4153-4341-9b58-e86bade25ffd",
"title": "Just Ok",
"rating": 2,
"gallery": [
{
"id": "1cb158af-0983-4bac-9e4f-0274b3836cdd",
"typeCode": "PHOTO"
},
{
"id": "aae64f19-22a8-4da7-b40a-fbbd8b2ef30b",
"typeCode": "PHOTO"
}
],
"reviewer": {
"memberId": "2acf2ea7-7a37-42d8-a019-3d9467cbdcd1",
},
"timestamp": {
"createdAt": "2011-03-30T09:52:36.000Z",
"updatedAt": "2011-03-30T09:52:36.000Z"
},
"isUserVerified": true,
}
And I would like to create a query for obtaining one of the gallery objects.
I have tried this but get both objects in the array:
SELECT jsonb_path_query(data->'gallery', '$[*]') AS content
FROM public.reviews
WHERE jsonb_path_query_first(data->'gallery', '$.id') ? '1cb158af-0983-4bac-9e4f-0274b3836cdd'
With this other query I get the first object:
SELECT jsonb_path_query_first(data->'gallery', '$[*]') AS content
FROM public.reviews
WHERE jsonb_path_query_first(data->'gallery', '$.id') ? '1cb158af-0983-4bac-9e4f-0274b3836cdd'
But filtering by the second array object id, I get no result:
SELECT jsonb_path_query_first(data->'gallery', '$[*]') AS content
FROM public.reviews
WHERE jsonb_path_query_first(data->'gallery', '$.id') ? 'aae64f19-22a8-4da7-b40a-fbbd8b2ef30b'
I have read the official documentation and tried other functions like jsonb_path_exists or jsonb_path_match on the where condition but was not able to make the query work.
Any help would be greatly appreciated. Thanks in advance.
I managed to get the query working as needed. Here is my proposal:
SELECT gallery
FROM public.reviews, jsonb_path_query(data->'gallery', '$[*]') as gallery
WHERE data->>'id' = '87b05c62-4153-4341-9b58-e86bade25ffd' and gallery->>'id' = 'aae64f19-22a8-4da7-b40a-fbbd8b2ef30b'
Hope it helps others.
I have a jsonb column with the following structure:
{
"key1": {
"type": "...",
"label": "...",
"variables": [
{
"label": "Height",
"value": 131315.9289,
"variable": "myVar1"
},
{
"label": "Width",
"value": 61085.7525,
"variable": "myVar2"
}
]
},
}
I want to query for the average height across all rows. The top-level key values are unknown, so I have something like this:
select id,
avg((latVars ->> 'value')::numeric) as avg
from "MyTable",
jsonb_array_elements((my_json_field->jsonb_object_keys(my_json_field)->>'variables')::jsonb) as latVars
where my_json_field is not null
group by id;
It's throwing the following error:
ERROR: set-returning functions must appear at top level of FROM
Moving the jsonb_array_elements function above MyTable in the FROM clause doesn't work.
I'm following the basic advice found in this SO answer to no avail.
Any advice?
jsonb_array_elements is not relevant until my_json_field is a json array at the top level.
You can use instead the jsonb_path_query function based on the jsonpath language if postgres >= 12 :
select id
, avg(v.value :: numeric) as avg
from "MyTable"
, jsonb_path_query(my_json_field, '$.*.variables[*] ? (#.label == "Height").value') AS v(value)
where my_json_field is not null
group by id;
I have a Postgres JSONB data which contains an ARRAY of type NUMERIC. I want to extract this ARRAY and store it in a variable of type NUMERIC[]. Here's is my JSONB object.
{
"userIds": [
101,102,103
],
"userRole": {
"id": "1",
"name": "Administrator"
}
}
How can I extract userIds from this JSONB object and store them in NUMERIC[] as I have to iterate on this NUMERIC[]?
Any help would be highly appreciated.
One way is to extract the ids with jsonb_array_elements, parse them to the right data type and aggregate them again in an array, e.g.:
SELECT array_agg(id) FROM (
SELECT
(jsonb_array_elements('{
"userIds": [101,102,103],
"userRole": {
"id": "1",
"name": "Administrator"
}
}'::jsonb->'userIds')::numeric)) j(id);
array_agg
---------------
{101,102,103}
(1 row)
If you want to iterate over these values as rows in your resultset, don't bother with the outer query:
SELECT
jsonb_array_elements('{
"userIds": [101,102,103],
"userRole": {
"id": "1",
"name": "Administrator"
}}'::jsonb->'userIds')::numeric;
jsonb_array_elements
----------------------
101
102
103
(3 rows)
I want to get a specific string from a column. How can I get that.
Here is the json with column name json with table name my_table
I want to fetch "extensionAttribute.simSerial": "310240000029929".
{
"name": "urn:imei:930000001801583",
"type": "DEVICE",
"sourceId": "P-n1000USCqT4",
"consumers": "CDM",
"crudStatus": {
"status": "SUCCESS",
"operation": "UPDATE"
},
"targetName": "urn:imei:930000001801583",
"deviceTypeId": "dgs11b74714f7020ctoogu3zfugc6",
"createdUserId": "a8aacc5d978d494eb54ae4243e714646",
"onboardStatus": "DONE",
"consrStatus": "",
"deviceTypeName": "performance_device_type_2",
"lwm2mPskSecret": "49443",
"createdUserName": "manager",
"bootstrapRequest": true,
"lwm2mPskIdentity": "urn:imei:930000001801583",
"boostrapPskSecret": "49443",
"deviceTypeVersion": 1,
"lastUpdatedUserId": "",
"lwm2mSecurityMode": "psk",
"consumersForUpdate": "",
"bootstrapPskIdentity": "urn:imei:930000001801583",
"pureCoapSecurityMode": "NONE",
"bootstrapSecurityMode": "psk",
"extensionAttribute.imsi": "310240000029929",
"extensionAttribute.msisdn": "310240000029929",
"extensionAttribute.simSerial": "310240000029929",
"extensionAttribute.msisdnStatus": "active"
}
Solution
You can do it as follows:
select column_name->>'extensionAttribute.simSerial' as simSerial from my_table;
where column_name is your column name in a table.
If you will have JSON with higher depth you can do something like:
column_name->'key_in_json'->'another_key_in_json'->>'last_key_in_json'
Manual
JSON Functions and Operators
PostgreSQL JSON Tutorial
SELECT * FROM some_table;
I can query to get the following results:
{
"sku0": {
"Id": "18418",
"Desc": "yes"
},
"sku1": {
"Id": "17636",
"Desc": "no"
},
"sku2": {
"Id": "206714",
"Desc": "yes"
},
"brand": "abc",
"displayName": "something"
}
First, the number of skus is not fixed. It may be sku0, sku1, sku2, sku3, sku4 ... but they all start with sku.
Then, I want to query Id with 17636 and determine whether its value of Desc is yes or no. After reading the PostgreSQL JSON Functions and Operators documentation, Depressing I didn't find a good way.
I can convert the result into a Python dictionary, and then use python's method can easily achieve my requirements.
If the requirements can also be achieved with postgresql statements, which method is more recommended than the Python dictionary?
I am not sure I completely understand what the result is you want. But if you want to filter on the Id, you need to unnest all the elements inside the JSON column:
select d.v ->> 'Desc' as description
from the_table t
cross join jsonb_each(t.data) as d(k,v)
where d.v ->> 'Id' = '17636'
You could use the new jsonpath notation of PostgreSQL v12:
SELECT data ## '$.* ? (#.Id == "17636").Desc == "yes"'
FROM some_table;
That will start with the root of data ($), find any attribute in it (*), filter only those attributes that contain an Id with value "17636", get their Desc attribute and return TRUE only if that attribute is "yes".
Nice, isn't it?
This will probably give you what you need.
select value->>'Desc' from jsonb_each('{
"sku0": {
"Id": "18418",
"Desc": "yes"
},
"sku1": {
"Id": "17636",
"Desc": "no"
},
"sku2": {
"Id": "206714",
"Desc": "yes"
},
"brand": "abc",
"displayName": "something"
}'::jsonb)
where key like 'sku%'
and value->>'Id'='17636'
Best regards,
Bjarni