I have a json column titled 'classifiers' with data like this:
[ { "category": "Building & Trades", "type": "Services"
, "subcategory": "Construction" } ]
I would like to pull each element and insert into columns on the same row titled, for example, 'category', 'type' and 'subcategory'.
This query pulls out what I want, in this case 'category':
SELECT parts->'category' AS category
FROM (SELECT json_array_elements(classifiers) AS parts FROM <tablename>) AS more_parts
I can't figure out the 'WHERE' part in an UPDATE/SET/WHERE type of query, for example:
UPDATE <table>
SET category = (SELECT parts->'category' AS category
FROM (SELECT json_array_elements(classifiers) AS parts
FROM <tablename>
) AS more_parts
) WHERE ???
Without WHERE multiple rows are returned.
I would like to pull each element and insert into columns on the same
row titled, for example, 'category', 'type' and 'subcategory'.
Sounds like you really want this:
UPDATE tbl
SET category = classifiers->0->'category'
,type = classifiers->0->'type'
,subcategory = classifiers->0->'subcategory'
Updates all rows. Requires Postgres 9.3+.
The first operator ->0 reverences the only object in the array (json array index starting from 0 unlike Postgres arrays, which start from 1 per default).
The second operator ->'category' gets the field from the object.
Refer to the manual here.
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 am attempting to update a jsonb column pagesRead on table Books which contains an array of objects. The structure of it looks similar to this:
[{
"book": "Moby Dick",
"pagesRead": [
"1",
"2",
"3",
"4"
]
},
{
"book": "Book Thief",
"pagesRead": [
"1",
"2"
]
}]
What I am trying to do is update the pagesRead when a specific page of the book is read or if someone has started a new book, add an extra entry into it.
I am able to retrieve the specific book details, but I am unsure about how to update it.
EDIT: So I had to use the Update query from S-Man to add a book entry, but I used the Insert query from Barbaros Özhan to handle updating the page
Some thoughts before:
You should never store structured data as it is in one column. This yields problems with updates, indexing (so, searching/performance), filtering, everything. Please normalize everything into proper tables and columns
You should never store arrays. Normalize it.
Do not use type text to store integer (pages)
"pagesRead" is a sibling of your filter element ("book"). This makes it much more complicated to reference it than referencing it as a child. So think about the book name (or better: an id) as key like {"my_id_for_book_thief": {"name" : "Book Thief", "pagesRead": [...]}}. In that case, you could use a path for referencing it. Otherwise, we need to extract the array, have a look into each book attribute and reference its sibling
demo:db<>fiddle
Adding a book is quite simple (Assuming that you are using type jsonb instead of type json):
SELECT mydata || '{"book": "Lord Of The Rings", "pagesRead": []}'
FROM mytable
Update:
UPDATE mytable
SET mycolumn = mycolumn || '{"book": "Lord Of The Rings", "pagesRead": []}'
Adding a pagesRead value:
SELECT
jsonb_agg( -- 4
jsonb_build_object( -- 3
'book', elem -> 'book',
'pagesRead', CASE WHEN elem ->> 'book' = 'Moby Dick' THEN -- 2
elem -> 'pagesRead' || '"42"'
ELSE elem -> 'pagesRead' END
)
) as new_array
FROM mytable,
jsonb_array_elements(mydata) as elem -- 1
Extract the array into one record per element
Add a page if element contains correct book
Rebuild the object
Reaggregate your array.
Update would be:
UPDATE mytable
SET mycolumn = s.new_array
FROM (
-- <query above>
) s
Assuming you want to add a new page for the second book (Book Thief), then using JSONB_INSERT() function with the following Update Statement will be enough
UPDATE books
SET pagesRead = JSONB_INSERT(pagesRead,'{1,pagesRead,1}','"3"'::JSONB,true)
But, in order to make it a dynamical solution, without knowing the position of the book within the main array, and adding the new page number to the end of the pagesRead array of the desired book, determine the position, and the related array's length within the subquery as
WITH b AS
(
SELECT idx-1 AS pos1,
JSONB_ARRAY_LENGTH( (j ->> 'pagesRead')::JSONB )-1 AS pos2
FROM books
CROSS JOIN JSONB_ARRAY_ELEMENTS(pagesRead)
WITH ORDINALITY arr(j,idx)
WHERE j ->> 'book' = 'Book Thief'
)
UPDATE books
SET pagesRead =
JSONB_INSERT(
pagesRead,
('{'||pos1||',pagesRead,'||pos2||'}')::TEXT[],
--# pos1 stands for the position within the main array
--# pos2 stands for the position within the related pagesRead array
'"3"'::JSONB, --# an arbitrary page number
true --# the new page value will be inserted after the target path
)
FROM b
Demo
I have following jsonb column which name is data in my sql table.
{
"special_note": "Some very long special note",
"extension_conditions": [
{
"condition_id": "5bfb8b8d-3a34-4cc3-9152-14139953aedb",
"condition_type": "OPTION_ONE"
},
{
"condition_id": "fbb60052-806b-4ae0-88ca-4b1a7d8ccd97",
"condition_type": "OPTION_TWO"
}
],
"floor_drawings_file": "137c3ec3-f078-44bb-996e-161da8e20f2b",
}
What I need to do is to update every object's field with name condition_type in extension_conditions array field from OPTION_ONE to MARKET_PRICE and OPTION_TWO leave the same.
Consider that this extension_conditions array field is optional so I need to filter rows where extension_conditions is null
I need a query which will update all my jsonb columns of rows of this table by rules described above.
Thanks in advance!
You can use such a statement containing JSONB_SET() function after determining the position(index) of the related key within the array
WITH j AS
(
SELECT ('{extension_conditions,'||idx-1||',condition_type}')::TEXT[] AS path, j
FROM tab
CROSS JOIN JSONB_ARRAY_ELEMENTS(data->'extension_conditions')
WITH ORDINALITY arr(j,idx)
WHERE j->>'condition_type'='OPTION_ONE'
)
UPDATE tab
SET data = JSONB_SET(data,j.path,'"MARKET_PRICE"',false)
FROM j
Demo 1
Update : In order to update for multiple elements within the array, the following query containing nested JSONB_SET() might be preferred to use
UPDATE tab
SET data =
(
SELECT JSONB_SET(data,'{extension_conditions}',
JSONB_AGG(CASE WHEN j->>'condition_type' = 'OPTION_ONE'
THEN JSONB_SET(j, '{condition_type}', '"MARKET_PRICE"')
ELSE j
END))
FROM JSONB_ARRAY_ELEMENTS(data->'extension_conditions') AS j
)
WHERE data #> '{"extension_conditions": [{"condition_type": "OPTION_ONE"}]}';
Demo 2
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 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.