device_id | device
-----------------------------
9809 | { "name" : "printer", "tags" : [] }
9810 | { "name" : "phone", "tags" : [{"count": 2, "price" : 77}, {"count": 3, "price" : 37} ] }
For the following postgres SQL query on a jsonb column "device" that contains array 'tags':
SELECT t.device_id, elem->>'count', elem->>'price'
FROM tbl t, json_array_elements(t.device->'tags') elem
where t.device_id = 9809
device_id is the primary key.
I have two issues that I don't know how to solve:
tags is an array field that may be empty, in which case I got 0 rows. I want output no matter tags is empty or not. Dummy values are ok.
If tags contain multiple elements, I got multiple rows for the same device id. How to aggregate those multiple elements into one row?
Your first problem can be solved by using a left outer join, that will substitute NULL values for missing matches on the right side.
The second problem can be solved with an aggregate function like json_agg, array_agg or string_agg, depending on the desired result type:
SELECT t.device_id,
jsonb_agg(elem->>'count'),
jsonb_agg(elem->>'price')
FROM tbl t
LEFT JOIN LATERAL jsonb_array_elements(t.device->'tags') elem
ON TRUE
GROUP BY t.device_id;
You will get a JSON array containing just null for those rows where the array is empty, I hope that is ok for you.
Related
I have a table in PostgreSQL
CREATE TABLE IF NOT EXISTS account_details
(
account_id integer,
condition json
);
And the data's present inside this table are
account_id
condition
1
[{"action":"read","subject":"rootcompany","conditions":{"rootcompanyid":{"$in":[35,20,5,6]}}}]
2
[{"action":"read","subject":"rootcompany","conditions":{"rootcompanyid":{"$in":[1,4,2,3,6]}}}]
3
[{"action":"read","subject":"rootcompany","conditions":{"rootcompanyid":{"$in":[5]}}}]
I need to fetch the details of all account having rootcompanyid in (5). IF part of any **rootcompanyid's ** are present in any of the account details should display the result.
So output should contain account_id --> 1 and 3 rows
The below query is fetching only the last row (account_id = 3) not the first row
SELECT *
FROM account_details
WHERE ((condition->0->>'conditions')::json->>'rootcompanyid')::json->>'$in' = '[5]';
Expected Output : IF part of any **rootcompanyid's ** are present in any of the account details should display the result.
account_id
condition
1
[{"action":"read","subject":"rootcompany","conditions":{"rootcompanyid":{"$in":[35,20,5,6]}}}]
3
[{"action":"read","subject":"rootcompany","conditions":{"rootcompanyid":{"$in":[5]}}}]
That's easily done with the JSON containment operator:
WHERE condition::jsonb #> '[ { "conditions": { "rootcompanyid": { "$in": [5] } } } ]'
If you want to search for more than a single array element, either use two of the above conditions with OR or use a JSONPATH query:
WHERE jsonb_path_exists(
condition::jsonb,
'$[*].conditions.rootcompanyid.\$in[*] ? (# == 5 || # == 6)'
)
I have a column of type jSONB that have data like this:
column name: used_filters
row number 1 example:
{ "categories" : ["economic", "Social"], "tags": ["world" ,"eco-friendly"] }
row number 2 example:
{ "categories" : ["economic"], "tags": ["eco-friendly"] , "keywords" : ["2050"] }
I want to group the result to get the most frequent value for each one of the keys
something like this:
key
most_freq
category
economic
tags
eco-friendly
keyword
2050
the keys are not constant and could be something other than the example I said but I know that they will be frequent.
You can extract keys and values as arrays first by using jsonb_each, and then unnest the generated arrays by jsonb_array_elements_text. The rest is classical aggregation along with sorting through the count values by window function such as
SELECT key, value
FROM ( SELECT j.key, jj.value,
RANK() OVER (PARTITION BY j.key ORDER BY COUNT(*) DESC)
FROM t,
LATERAL jsonb_each(js) AS j,
LATERAL jsonb_array_elements_text(j.value) AS jj
GROUP BY j.key, jj.value ) AS q
WHERE rank = 1
Demo
I have a Postgres table timeline with two columns:
user_id (varchar)
items (json)
This is the structure of items json field:
[
{
itemId: "12345",
text: "blah blah"
},
//more items with itemId and text
]
I need to delete all the items where itemId equals a given value. e.g. 12345
I have this working SQL:
UPDATE timeline
SET items = items::jsonb - cast((
SELECT position - 1 timeline, jsonb_array_elements(items::jsonb)
WITH ORDINALITY arr(item_object, position)
WHERE item_object->>'itemId' = '12345') as int)
It works fine. It only fails when no items are returned by the subquery i.e. when there are no items whose itemId equals '12345'. In those cases, I get this error:
null value in column "items" violates not-null constraint
How could I solve this?
Try this:
update timeline
set items=(select
json_agg(j)
from json_array_elements(items) j
where j->>'itemId' not in ( '12345')
);
DEMO
The problem is that when null is passed to the - operator, it results in null for the expression. That not only violates your not null constraint, but it is probably also not what you are expecting.
This is a hack way of getting past it:
UPDATE timeline
SET items = items::jsonb - coalesce(
cast((
SELECT position - 1 timeline, jsonb_array_elements(items::jsonb)
WITH ORDINALITY arr(item_object, position)
WHERE item_object->>'itemId' = '12345') as int), 99999999)
A more correct way to do it would be to collect all of the indexes you want to delete with something like the below. If there is the possibility of more than one userId: 12345 within a single user_id row, then this will either fail or mess up your items(I have to test to see which), but at least it updates only rows with the 12345 records.
WITH deletes AS (
SELECT t.user_id, e.rn - 1 as position
FROM timeline t
CROSS JOIN LATERAL JSONB_ARRAY_ELEMENTS(t.items)
WITH ORDINALITY as e(jobj, rn)
WHERE e.jobj->>'itemId' = '12345'
)
UPDATE timeline
SET items = items - d.position
FROM deletes d
WHERE d.user_id = timeline.user_id;
I have jsonb in one of my table
the jsonb looks like this
my_data : [
{pid: 1, stock: 500},
{pid: 2, stock: 1000},
...
]
pid refers to products' table id ( which is pid )
EDIT: The table products has following properties: pid (PK), name
I want to loop over my_data[] in my JSONB and fetch pid's name from product table.
I need the result to look something like this (including the product names from the second table) ->
my_data : [
{
product_name : "abc",
pid: 1,
stock : 500
},
...
]
How should I go about performing such jsonb inner join?
Edit :- tried S-Man's solutions and i'm getting this error
"invalid reference to FROM-clause entry for table \"jc\""
here is the
SQL QUERY
step-by-step demo:db<>fiddle
SELECT
jsonb_build_object( -- 5
'my_data',
jsonb_agg( -- 4
elems || jsonb_build_object('product_name', mot.product_name) -- 3
)
)
FROM
mytable,
jsonb_array_elements(mydata -> 'my_data') as elems -- 1
JOIN
my_other_table mot ON (elems ->> 'pid')::int = mot.pid -- 2
Expand JSON array into one row per array element
Join the other table against the current one using the pid values (notice the ::int cast, because otherwise it would be text value)
The new columns from the second table now can be converted into a JSON object. This one can be concatenate onto the original one using the || operator
After that recreating the array from the array elements again
Putting this in array into a my_data element
Another way is using jsonb_set() instead of step 5 do reset the array into the original array directly:
step-by-step demo:db<>fiddle
SELECT
jsonb_set(
mydata,
'{my_data}',
jsonb_agg(
elems || jsonb_build_object('product_name', mot.product_name)
)
)
FROM
mytable,
jsonb_array_elements(mydata -> 'my_data') as elems
JOIN
my_other_table mot ON (elems ->> 'pid')::int = mot.pid
GROUP BY mydata
Working in a Rails App, I have the following table structure (pertinent columns only)
Photos (id: integer)
Taggings (photo_id: integer, tag_id: integer)
Tags (id: integer, name:string)
I have the following SQL query:
SELECT distinct photos.*
FROM \"photos\" INNER JOIN \"taggings\" ON \"photos\".\"id\" = \"taggings\".\"photo_id\"
INNER JOIN \"tags\" ON \"tags\".\"id\" = \"taggings\".\"tag_id\"
WHERE \"tags\".\"name\" IN ('foo', 'bar')
When I generate this query I'm passing in an array of tags (in this case ["foo","bar"]). The query correctly searches for photos that match ANY of the tags passed in the array.
How can I change this query to select records with ALL of the given tags (ie a photo only matches if tagged with "foo" AND "bar", instead of selecting records with ANY of the given tags?
There may be a better way, but this should do it
SELECT photos.id,max(otherColumn)
FROM \"photos\"
INNER JOIN \"taggings\"
ON \"photos\".\"id\" = \"taggings\".\"photo_id\"
INNER JOIN \"tags\"
ON \"tags\".\"id\" = \"taggings\".\"tag_id\"
WHERE \"tags\".\"name\" IN ('foo', 'bar')
group by photos.id
having count(*) = 2 --2 is the number of items in your array of tags.
If you are in rails you don't need query to do this.
Tags.find(1).taggings should give you an array of all photos with that tag
you can also use Tags.find_by_name("foo").taggings
you can similarly iterate over all tags, and collect the arrays and then just do something like on the arrays you have got.
[ 1, 1, 3, 5 ] & [ 1, 2, 3 ] #=> [ 1, 3 ]
Basically 'and' the arrays and get the unique photos.This way you can get the photos that match all the tags.