Each record in my database has a json list, from which I'm trying to return a value inside each element.
I'm trying to return
environmental services, energy & utilities
From
[
{
"key": "environmental services"
},
{
"key": "energy & utilities"
}
]
And.
construction
From
[
{
"key": "construction"
}
]
Where the length of each json list in each record is undetermined.
I can get the first value with:
select
column_name -> 0 -> 'key'
from table
But how to get all.
How can I do this in postgresql?
Use the function jsonb_array_elements() in a lateral join to get all elements of the arrays and the aggregate function string_agg():
with my_table(json_col) as (
values
('[
{
"key": "environmental services"
},
{
"key": "energy & utilities"
}
]'::jsonb),
('[
{
"key": "construction"
}
]')
)
select string_agg(value->>'key', ', ')
from my_table
cross join jsonb_array_elements(json_col)
group by json_col -- use PK here (if exists)
string_agg
--------------------------------------------
environmental services, energy & utilities
construction
(2 rows)
Related
My Postgres DB Table BookingDetails has columns - id(bigint), info(jsonb)
My Json structure:
"bookingType": “special”,
“travellers”: [
{
"id": 1,
"nationality": "SomeValue",
}
],
“someTag”: “abc”
}
The travellers here is an array (and in this example, there’s only one element)
I want to:
Select records where nationality=‘CertainValue’
Update records set nationality=‘AnotherValue’ where nationality=‘CertainValue’
I could retrieve the array using:
select CAST (info->'travellers' AS TEXT) from BookingDetails
[
{
"id": 1,
"nationality": "SomeValue",
}
]
I could retrieve the array first element using:
select CAST (info->'travellers'->>0 AS TEXT) from BookingDetails
{
"id": 1,
"nationality": "SomeValue"
}
But how to do a select based on nationality=‘CertainValue’?
try this :
SELECT jsonb_set(info, array['travellers', (a.id - 1) :: text, 'nationality'], to_jsonb('AnotherValue' :: text))
FROM BookingDetails
CROSS JOIN LATERAL jsonb_array_elements(info->'travellers') WITH ORDINALITY AS a(content, id)
WHERE a.content->>'nationality' = 'CertainValue'
see the test result in dbfiddle
I want to remove a JSONB object by their unique 'id' value from a JSONB array. I am no expert at writing SQL code, but I managed to write the concatenate function.
For an example: Remove this object from an array below.
{
"id": "ad26e2be-19fd-4862-8f84-f2f9c87b582e",
"title": "Wikipedia",
"links": [
"https://en.wikipedia.org/1",
"https://en.wikipedia.org/2"
]
},
Schema:
CREATE TABLE users (
url text not null,
user_id SERIAL PRIMARY KEY,
name VARCHAR,
list_of_links jsonb default '[]'
);
list_of_links format:
[
{
"id": "ad26e2be-19fd-4862-8f84-f2f9c87b582e",
"title": "Wikipedia",
"links": [
"https://en.wikipedia.org/1",
"https://en.wikipedia.org/2"
]
},
{
"id": "451ac172-b93e-4158-8e53-8e9031cfbe72",
"title": "Russian Wikipedia",
"links": [
"https://ru.wikipedia.org/wiki/",
"https://ru.wikipedia.org/wiki/"
]
},
{
"id": "818b99c8-479b-4846-ac15-4b2832ec63b5",
"title": "German Wikipedia",
"links": [
"https://de.wikipedia.org/any",
"https://de.wikipedia.org/any"
]
},
...
]
The concatenate function:
update users set list_of_links=(
list_of_links || (select *
from jsonb_array_elements(list_of_links)
where value->>'id'='ad26e2be-19fd-4862-8f84-f2f9c87b582e'
)
)
where url='test'
returning *
;
Your json data is structured so you have to unpack it, operate on the unpacked data, and then repack it again:
SELECT u.url, u.user_id, u.name,
jsonb_agg(
jsonb_build_object('id', l.id, 'title', l.title, 'links', l.links)
) as list_of_links
FROM users u
CROSS JOIN LATERAL jsonb_to_recordset(u.list_of_links) AS l(id uuid, title text, links jsonb)
WHERE l.id != 'ad26e2be-19fd-4862-8f84-f2f9c87b582e'::uuid
GROUP BY 1, 2, 3
The function jsonb_to_recordset is a set-returning function so you have to use it as a row source, joined to its originating table with the LATERAL clause so that the list_of_links column is available to the function to be unpacked. Then you can delete the records you are not interested in using the WHERE clause, and finally repack the structure by building the record fields into a jsonb structure and then aggregating the individual records back into an array.
I wrote this on JS but that does not matter to how it works. Essentially, its getting all the items from the array, then finding the matching id which returns an index. And using that index, I use "-" operator which takes the index and removes it from the array. Sorry if my grammar is bad.
//req.body is this JSON object
//{"url":"test", "id": "ad26e2be-19fd-4862-8f84-f2f9c87b582e"}
var { url, id } = req.body;
pgPool.query(
`
select list_of_links
from users
where url=$1;
`,
[url],
(error, result) => {
//block code executing further if error is true
if (error) {
res.json({ status: "failed" });
return;
}
if (result) {
// this function just returns the index of the array element where the id matches from request's id
// 0, 1, 2, 3, 4, 5
var index_of_the_item = result.rows.list_of_links
.map(({ id: db_id }, index) =>
db_id === id ? index : false
)
.filter((x) => x !== false)[0];
//remove the array element by it's index
pgPool.query(
`
update users
set list_of_links=(
list_of_links - $1::int
)
where url=$2
;
`,
[index_of_the_item, url], (e, r) => {...}
);
}
}
);
I am constructing an interface between a PostgreSQL system and a SQL Server system and am attempting to "flatten" the structure of the JSON data to facilitate this. I'm very experienced in SQL Server but I'm new to both PostgreSQL and JSON.
The JSON contains essentially two types of structure: those of type "text" or "textarea" where the value I want is in an object named value (the first two cases below) and those of type "select" where the value object points to an id object in a lower-level options array (the third case below).
{
"baseGroupId": {
"fields": [
{
"id": "1f53",
"name": "Location",
"type": "text",
"options": [],
"value": "Over the rainbow"
},
{
"id": "b547",
"name": "Description",
"type": "textarea",
"options": [],
"value": "A place of wonderful discovery"
},
{
"id": "c12f",
"name": "Assessment",
"type": "select",
"options": [
{
"id": "e5fd",
"name": "0"
},
{
"id": "e970",
"name": "1"
},
{
"id": "0ff4",
"name": "2"
},
{
"id": "2db3",
"name": "3"
},
{
"id": "241f",
"name": "4"
},
{
"id": "3f52",
"name": "5"
}
],
"value": "241f"
}
]
}
}
Those with a sharp eye will see that the value of the last value object "241f" can also be seen within the options array against one of the id objects. When nested like this I need to extract the value of the corresponding name, in this case "4".
The JSON-formatted information is in table customfield field textvalue. It's datatype is text but I'm coercing it to json. I was originally getting array set errors when trying to apply the criteria in a WHERE clause and then I read about using a LATERAL subquery instead. It now runs but returns all the options, not just the one matching the value.
I'm afraid I couldn't get an SQL Fiddle working to reproduce my results, but I would really appreciate an examination of my query to see if the problem can be spotted.
with cte_custombundledfields as
(
select
textvalue
, cfname
, json_array_elements(textvalue::json -> 'baseGroupId'->'fields') ->> 'name' as name
, json_array_elements(textvalue::json -> 'baseGroupId'->'fields') ->> 'value' as value
, json_array_elements(textvalue::json -> 'baseGroupId'->'fields') ->> 'type' as type
from
customfield
)
, cte_custombundledfieldsoptions as
(
select *
, json_array_elements(json_array_elements(textvalue::json -> 'baseGroupId'->'fields') -> 'options') ->> 'name' as value2
from
cte_custombundledfields x
, LATERAL json_array_elements(x.textvalue::json -> 'baseGroupId'->'fields') y
, LATERAL json_array_elements(y -> 'options') z
where
type = 'select'
and z ->> 'id' = x.value
)
select *
from
cte_custombundledfieldsoptions
I posted a much-simplified rewrite of this question which was answered by Bergi.
How do I query a string from JSON based on another string within the JSON in PostgreSQL?
I'm using Presto and trying to extract all 'id' from 'source'='dd' from a nested json structure as following.
{
"results": [
{
"docs": [
{
"id": "apple1",
"source": "dd"
},
{
"id": "apple2",
"source": "aa"
},
{
"id": "apple3",
"source": "dd"
}
],
"group": 99806
}
]
}
expected to extract the ids [apple1, apple3] into a column in Presto
I am wondering what is the right way to achieve this in Presto Query?
If your data has a regular structure as in the example you posted, you can use a combination of parsing the value as JSON, casting it to a structured SQL type (array/map/row) and the using array processing functions to filter, transform and extract the elements you want:
WITH data(value) AS (VALUES '{
"results": [
{
"docs": [
{
"id": "apple1",
"source": "dd"
},
{
"id": "apple2",
"source": "aa"
},
{
"id": "apple3",
"source": "dd"
}
],
"group": 99806
}
]
}'),
parsed(value) AS (
SELECT cast(json_parse(value) AS row(results array(row(docs array(row(id varchar, source varchar)), "group" bigint))))
FROM data
)
SELECT
transform( -- extract the id from the resulting docs
filter( -- filter docs with source = 'dd'
flatten( -- flatten all docs arrays into a single doc array
transform(value.results, r -> r.docs) -- extract the docs arrays from the result array
),
doc -> doc.source = 'dd'),
doc -> doc.id)
FROM parsed
The query above produces:
_col0
------------------
[apple1, apple3]
(1 row)
Given this dataset:
[
{
"dataChannelId": 8516,
"measures": [
{
"dateTime": "2019-01-01T12:00:00",
},
{
"dateTime": "2019-01-02T12:00:00",
}
}]
And this query:
WITH
temp AS
(
SELECT
dataChannelId,
arrayElement.ArrayValue as element
FROM GriegInputStream
CROSS APPLY GetArrayElements([mesurasdfes]) AS arrayElement
)
SELECT
temp.dataChannelId as sensorId, temp.element.dateTime, temp.element.value,temp.element.unit,temp.element.maxValue, temp.element.minValue
INTO
Sensoroutput
FROM
temp
I get invalid column name, does not exist on dataChannelId, but measures seem to work fine. How can I access this value without stream analytics complaining?
Your sample json data lack a square bracket ].
sample data:
[
{
"dataChannelId": 8516,
"measures": [
{
"dateTime": "2019-01-01T12:00:00",
},
{
"dateTime": "2019-01-02T12:00:00",
}
]
}
]
Query sql:
WITH
temp AS
(
SELECT
jsoninput.dataChannelId,
arrayElement.ArrayValue as element
FROM jsoninput
CROSS APPLY GetArrayElements(jsoninput.measures) AS arrayElement
)
SELECT
temp.dataChannelId as sensorId, temp.element.dateTime
INTO
Sensoroutput
FROM
temp
Output: