I have the following JSON stored in a PostgreSQL JSON column
{
"status": "Success",
"message": "",
"data": {
"serverIp": "XXXX",
"ruleId": 32321,
"results": [
{
"versionId": 555555,
"PriceID": "8abf35ec-3e0e-466b-a4e5-2af568e90eec",
"price": 550,
"Convert": 0.8922953080331764,
"Cost": 10
}
]
}
}
I would like to search for a specific priceID across the entire JSON column (name info) and select the entire results element by the PriceID.
How do i do that in postgresql JSON?
One option uses exists and json(b)_array_elements(). Assuming that your table is called mytable and that the jsonb column is mycol, this would look like:
select t.*
from mytable t
where exists (
select 1
from jsonb_array_elements(t.mycol -> 'data' -> 'results') x(elt)
where x.elt ->> 'PriceID' = '8abf35ec-3e0e-466b-a4e5-2af568e90eec'
)
In the subquery, jsonb_array_elements() unnest the json array located at the given path. Then, the where clause ensures that at least one elment in the array has the given PriceID.
If your data is of json datatype rather than jsonb, you need to use json_array_elements() instead of jsonb_array_elements().
If you want to display some information coming from the matching array element, then it is different. You can use a lateral join instead of exists. Keep in mind, though, that this will duplicate the rows if more than one array element matches:
select t.*, x.elt ->> 'price' price
from mytable t
cross join lateral jsonb_array_elements(t.mycol -> 'data' -> 'results') x(elt)
where x.elt ->> 'PriceID' = '8abf35ec-3e0e-466b-a4e5-2af568e90eec'
Related
Assume i have a table called MyTable and this table have a JSON type column called myjson and this column have next value as a json array hold multiple objects, for example like next:
[
{
"budgetType": "CF",
"financeNumber": 1236547,
"budget": 1000000
},
{
"budgetType": "ENVELOPE",
"financeNumber": 1236888,
"budget": 2000000
}
]
So how i can search if the record has any JSON objects inside its JSON array with financeNumber=1236547
Something like this:
SELECT
t.*
FROM
"MyTable",
LATERAL json_to_recordset(myjson) AS t ("budgetType" varchar,
"financeNumber" int,
budget varchar)
WHERE
"financeNumber" = 1236547;
Obviously not tested on your data, but it should provide a starting point.
with a as(
SELECT json_array_elements(myjson)->'financeNumber' as col FROM mytable)
select exists(select from a where col::text = '1236547'::text );
https://www.postgresql.org/docs/current/functions-json.html
json_array_elements return setof json, so you need cast.
Check if a row exists: Fastest check if row exists in PostgreSQL
I have create table with Json datatype field in PostgreSQL.
Also i have inserted data with multiple object in json data
like this
[
{
"Type": "1",
"Amount": "1000",
"Occurrence": 2,
"StartDate": "1990-01-19",
"EndDate": "1999-04-03"
},
{
"Type": "2",
"Amount": "2000",
"Occurrence": 2,
"StartDate": "1984-11-19",
"EndDate": "1997-09-29"
}
]
Now i have to retrieve my data as per below formate in single row like string_agg() function output.
Type Amount
1--2 1000-2000
also i have checked inbuilt function for json in PostgreSQL (https://www.postgresqltutorial.com/postgresql-json/) but not find any solutions for the same.
You will have to unnest the array and aggregate the individual keys:
The following assumes you have some kind of primary key column on the table (in addition to your JSON column):
select t.id,
string_agg(x.element ->> 'Type', '-') as types,
string_agg(x.element ->> 'Amount', '-') as amounts
from the_table t
cross join jsonb_array_elements(t.data) as x(element)
group by t.id;
jsonb_array_elements() extracts each array element and the main query then aggregates that back per ID using string_agg().
The above assumes your column is defined with the type jsonb (which it should be). If it is not, you need to use json_array_elements() instead.
Online example
I have a table mytable and a JSONB column employees that contains data like this:
[ {
"name":"Raj",
"email":"raj#gmail.com",
"age":32
},
{
"name":"Mohan",
"email":"Mohan#yahoo.com",
"age":21
}
]
I would like to extract only the names and save them in a list format, so the resulting cell would look like this:
['Raj','Mohan']
I have tried
select l1.obj ->> 'name' names
from mytable t
cross join jsonb_array_elements(t.employees) as l1(obj)
but this only returns the name of the first array element.
How do I get the name of all array elements?
Thanks!
PostgreSQL 11.8
In Postgres 12, you can use jsonb_path_query_array():
select jsonb_path_query_array(employees, '$[*].name') as names
from mytable
In earlier versions you need to unnest then aggregate back:
select (select jsonb_agg(e -> 'name')
from jsonb_array_elements(employees) as t(e)) as names
from mytable
I have the below sample JSON:
{
"Id1": {
"name": "Item1.jpg",
"Status": "Approved"
},
"Id2": {
"name": "Item2.jpg",
"Status": "Approved"
}
}
and I am trying to get the following output:
_key name Status
Id1 Item1.jpg Approved
Id2 Item2.jpg Approved
Is there any way I can achieve this in Snowflake using SQL?
You should use Snowflake's VARIANT data type in any column holding JSON data. Let's break this down step by step:
create temporary table FOO(v variant); -- Temp table to hold the JSON. Often you'll see a variant column simply called "V"
-- Insert into the variant column. Parse the JSON because variants don't hold string types. They hold semi-structured types.
insert into FOO select parse_json('{"Id1": {"name": "Item1.jpg", "Status": "Approved"}, "Id2": {"name": "Item2.jpg", "Status": "Approved"}}');
-- See how it looks in its raw state
select * from FOO;
-- Flatten the top-level JSON. The flatten function breaks down the JSON into several usable columns
select * from foo, lateral flatten(input => (foo.v)) ;
-- Now traverse the JSON using the column name and : to get to the property you want. Cast to string using ::string.
-- If you must have exact case on your column names, you need to double quote them.
select KEY as "_key",
VALUE:name::string as "name",
VALUE:Status::string as "Status"
from FOO, lateral flatten(input => (FOO.V)) ;
I have searched extensively (in Postgres docs and on Google and SO) to find examples of JSON functions being used on actual JSON columns in a table.
Here's my problem: I am trying to extract key values from an array of JSON objects in a column, using jsonb_to_recordset(), but get syntax errors. When I pass the object literally to the function, it works fine:
Passing JSON literally:
select *
from jsonb_to_recordset('[
{ "id": 0, "name": "400MB-PDF.pdf", "extension": ".pdf",
"transferId": "ap31fcoqcajjuqml6rng"},
{ "id": 0, "name": "1000MB-PDF.pdf", "extension": ".pdf",
"transferId": "ap31fcoqcajjuqml6rng"}
]') as f(name text);`
results in:
400MB-PDF.pdf
1000MB-PDF.pdf
It extracts the value of the key "name".
Here's the JSON in the column, being extracted using:
select journal.data::jsonb#>>'{context,data,files}'
from journal
where id = 'ap32bbofopvo7pjgo07g';
resulting in:
[ { "id": 0, "name": "400MB-PDF.pdf", "extension": ".pdf",
"transferId": "ap31fcoqcajjuqml6rng"},
{ "id": 0, "name": "1000MB-PDF.pdf", "extension": ".pdf",
"transferId": "ap31fcoqcajjuqml6rng"}
]
But when I try to pass jsonb#>>'{context,data,files}' to jsonb_to_recordset() like this:
select id,
journal.data::jsonb#>>::jsonb_to_recordset('{context,data,files}') as f(name text)
from journal
where id = 'ap32bbofopvo7pjgo07g';
I get a syntax error. I have tried different ways but each time it complains about a syntax error:
Version:
PostgreSQL 9.4.10 on x86_64-unknown-linux-gnu, compiled by gcc (Ubuntu 4.8.2-19ubuntu1) 4.8.2, 64-bit
The expressions after select must evaluate to a single value. Since jsonb_to_recordset returns a set of rows and columns, you can't use it there.
The solution is a cross join lateral, which allows you to expand one row into multiple rows using a function. That gives you single rows that select can act on. For example:
select *
from journal j
cross join lateral
jsonb_to_recordset(j.data#>'{context, data, files}') as d(id int, name text)
where j.id = 'ap32bbofopvo7pjgo07g'
Note that the #>> operator returns type text, and the #> operator returns type jsonb. As jsonb_to_recordset expects jsonb as its first parameter I'm using #>.
See it working at rextester.com
jsonb_to_recordset is a set-valued function and can only be invoked in specific places. The FROM clause is one such place, which is why your first example works, but the SELECT clause is not.
In order to turn your JSON array into a "table" that you can query, you need to use a lateral join. The effect is rather like a foreach loop on the source recordset, and that's where you apply the jsonb_to_recordset function. Here's a sample dataset:
create table jstuff (id int, val jsonb);
insert into jstuff
values
(1, '[{"outer": {"inner": "a"}}, {"outer": {"inner": "b"}}]'),
(2, '[{"outer": {"inner": "c"}}]');
A simple lateral join query:
select id, r.*
from jstuff
join lateral jsonb_to_recordset(val) as r("outer" jsonb) on true;
id | outer
----+----------------
1 | {"inner": "a"}
1 | {"inner": "b"}
2 | {"inner": "c"}
(3 rows)
That's the hard part. Note that you have to define what your new recordset looks like in the AS clause -- since each element in our val array is a JSON object with a single field named "outer", that's what we give it. If your array elements contain multiple fields you're interested in, you declare those in a similar manner. Be aware also that your JSON schema needs to be consistent: if an array element doesn't contain a key named "outer", the resulting value will be null.
From here, you just need to pull the specific value you need out of each JSON object using the traversal operator as you were. If I wanted only the "inner" value from the sample dataset, I would specify select id, r.outer->>'inner'. Since it's already JSONB, it doesn't require casting.