Let's assume I have a PostgreSQL table with following schema:
id: 1,
attribute_a: 'value'
attribute_b: 'value'
data: { attribute_c: 'value', array_of_values: [1,2,3] }
Where data is stored in a JSON structure. Is that possible to order the elements in the table by array_of_values length?
Use json_array_length() or jsonb_array_length() like Eggplant commented. Assuming jsonb:
SELECT *
FROM tbl
ORDER BY jsonb_array_length(data -> 'array_of_values')
BTW, the syntax for your JSON value should be:
{"attribute_c": "value", "array_of_values": [1, 2, 3]}
Related
I am struggling to conditionally extract values from a nested JSON string in the Mysql table.
{"users": [{"userId": "10000001", "userToken": "11000000000001", "userTokenValidity": 1}, {"userId": "10000002", "userToken": "12000000000001", "userTokenValidity": 1}, {"userId": "10000003", "userToken": "13000000000001", "userTokenValidity": 0}]}
I want to select a userToken but only if the userTokenValidity is 1. So in this example only "11000000000001" and "12000000000001" should get selected.
This will extract the whole array ... how should I filter the result?
SELECT t.my_column->>"$.users" FROM my_table t;
SELECT CAST(value AS CHAR) output
FROM test
CROSS JOIN JSON_TABLE(test.data, '$.users[*]' COLUMNS (value JSON PATH '$')) jsontable
WHERE value->>'$.userTokenValidity' = 1
https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=4876ec22a9df4f6d2e75a476a02a2615
I have a json like:
'attributes':[
{'attribute_name': 'name1','weight' = 10},
{'attribute_name': 'name2','weight' = 5},
...
]
}
Assuming all the attribute_name in the JSON are columns in a table. How to select only those columns from a table
In PostgreSql I can't find in the docs a function that could allow me to combine n json entities, whilst summing the value part in case of existing key/value pair
English not being my main language, I suspect I don't know how to search with the right terms
In other words
from a table with 2 columns
name data
'didier' {'vinyl': 2, 'cd': 3)
'Anne' {'cd' : 1, 'tape' : 4}
'Pierre' {'cd' : 1, 'tape': 9, 'mp3':2}
I want to produce the following result :
{ 'vinyl' : 2, 'cd' : 5, 'tape':13, mp3 : 2}
With is a "combine and sum" function
Thanks in advance for any idea
Didier
Using the_table CTE for illustration, first 'normalize' data column then sum per item type (k) and finally aggregate into a JSONB object.
with the_table("name", data) as
(
values
('didier', '{"vinyl": 2, "cd": 3}'::jsonb),
('Anne', '{"cd" : 1, "tape" : 4}'),
('Pierre', '{"cd" : 1, "tape": 9, "mp3":2}')
)
select jsonb_object_agg(k, v) from
(
select lat.k, sum((lat.v)::integer) v
from the_table
cross join lateral jsonb_each(data) as lat(k, v)
group by lat.k
) t;
-- {"cd": 5, "mp3": 2, "tape": 13, "vinyl": 2}
I am using JSON_MODIFY to build complex JSON. Moving from MySQL I am struggling with the JSON functions provided by SQL Server. The issue I'm having is that SQL Server seems to construct all JSON objects in an array. There is the WITHOUT_ARRAY_WRAPPER mechanism, which seems like it should do what I want, however; there are two undesirable consequences.
It only returns one result depending on how it is used
The result is a single string with escape characters
I have constructed a simple query which illustrates my needs and the issue.
QUERY 1
SELECT JSON_MODIFY(
JSON_QUERY('{"definitions": {"id": "INT", "name": "VARCHAR(23)"}}'),
'append $.data',
(
SELECT * FROM (
SELECT 1 AS id, '123abc' AS "name" UNION
SELECT 2 AS id, '234bcd' AS "name"
) AS "data"
FOR JSON PATH, WITHOUT_ARRAY_WRAPPER
)
) AS "data";
OUTPUT 1
{
"definitions":{
"id":"INT",
"name":"VARCHAR(23)"
},
"data":[
"{\"id\":1,\"name\":\"123abc\"},{\"id\":2,\"name\":\"234bcd\"}"
]
}
QUERY 2
SELECT JSON_MODIFY(
JSON_QUERY('{"definitions": {"id": "INT", "name": "VARCHAR(23)"}}'),
'append $.data',
(
SELECT * FROM (
SELECT 1 AS id, '123abc' AS "name" UNION
SELECT 2 AS id, '234bcd' AS "name"
) AS "data"
FOR JSON PATH
)
) AS "data";
OUTPUT 2
{
"definitions":{
"id":"INT",
"name":"VARCHAR(23)"
},
"data":[
[
{"id":1, "name":"123abc"},
{"id":2, "name":"234bcd"}
]
]
}
QUERY 1
The data object is an array (which is expected), but the problem is what is in the array... A single string with escape characters.
QUERY 2
The data object is an array, which contains an array. In order to access the actual array of data, I would use something like for each obj in data[0].... The problem this poses is, for anyone consuming the JSON object, I would have to tell them:
"In this particular object the data element is an array of
arrays--You'll want to use the first and only the first
element to access the actual array of data."
I've naively tried many different combinations of JSON_MODIFY, JSON_QUERY, and CONCAT to no avail. How can I properly use JSON_MODIFY to get the following output, without the double array in data?
{
"definitions":{
"id":"INT",
"name":"VARCHAR(23)"
},
"data":[
{"id":1, "name":"123abc"},
{"id":2, "name":"234bcd"}
]
}
You are over-thinking this by trying to JSON_MODIFY an existing object.
Construct the definitions and data properties that you need, inside a subquery if necessary.
Then use FOR JSON a second time to get the outer object.
SELECT
definitions = JSON_QUERY('{"id": "INT", "name": "VARCHAR(23)"}'),
data =
(
SELECT id, name
FROM (VALUES
(1, '123abc'),
(2, '234bcd')
) v(id, name)
FOR JSON PATH
)
FOR JSON PATH;
SQL Fiddle
By trial and error, I found the solution.
Removed the append keyword from the path parameter in the JSON_MODIFY statement
Removed the WITHOUT_ARRAY_WRAPPER parameter from the FOR JSON statement.
Now the results are as expected and I don't need to explain to any consumers to "Just use data[0]"
The Query
SELECT JSON_MODIFY(
JSON_QUERY('{"definitions": {"id": "INT", "name": "VARCHAR(23)"}}'),
'$.data',
(
SELECT * FROM (
SELECT 1 AS id, '123abc' AS "name" UNION
SELECT 2 AS id, '234bcd' AS "name"
) AS "data"
FOR JSON PATH
)
) AS "data";
Produces the following output
{
"definitions":{
"id":"INT",
"name":"VARCHAR(23)"
},
"data":[
{"id":1, "name":"123abc"},
{"id":2, "name":"234bcd"}
]
}
I am working on converting XML to j son string using the PostgreSQL.
we have attributecentric XML and would like to know how to convert it to j son.
Example XML:
<ROOT><INPUT id="1" name="xyz"/></ROOT>
Need to get the j son as follows:
{ "ROOT": { "INPUT": { "id": "1", "name": "xyz" }}}
got the above json format from an online tool.
any help or guidance will be appreciated.
Regards
Abdul Azeem
Basically, breakdown of this problem is the following:
extract values from given XML using xpath() function
generate and combine JSON entries using json_object_agg() function
The only tricky thing here is to combine key,value pairs together from xpath()/json_object_agg() results, which are{ "id": "1"} and { "name" : "xyz"}.
WITH test_xml(data) AS ( VALUES
('<ROOT><INPUT id="1" name="xyz"/></ROOT>'::XML)
), attribute_id(value) AS (
-- get '1' value from id
SELECT (xpath('//INPUT/#id',test_xml.data))[1] AS value
FROM test_xml
), attribute_name(value) AS (
-- get 'xyz' value from name
SELECT (xpath('//INPUT/#name',test_xml.data))[1] AS value
FROM test_xml
), json_1 AS (
-- generate JSON 1 {"id": "1"}
SELECT json_object_agg('id',attribute_id.value) AS payload
FROM attribute_id
), json_2 AS (
-- generate JSON 2 {"name" : "xyz"}
SELECT json_object_agg('name',attribute_name.value) AS payload FROM attribute_name
), merged AS (
-- Generate INPUT result - Step 1 - combine JSON 1 and 2 as single key,value source
SELECT key,value
FROM json_1,json_each(json_1.payload)
UNION ALL
SELECT key,value
FROM json_2,json_each(json_2.payload)
), input_json_value AS (
-- Generate INPUT result - Step 2 - use json_object_agg to create JSON { "id" : "1", "name" : "xyz" }
SELECT json_object_agg(merged.key,merged.value) AS data
FROM merged
), input_json AS (
-- Generate INPUT JSON as expected { "INPUT" : { "id" : "1", "name" : "xyz" } }
SELECT json_object_agg('INPUT',input_json_value.data) AS data
FROM input_json_value
)
-- Generate final reult
SELECT json_object_agg('ROOT',input_json.data)
FROM input_json;