I'm working on a live music database and I can't think of how to do a query that gets artists that have events on.
I have two tables: artist (containing id, name, description, etc.) and event_artist (many to many relationship) having artist_id and event_id columns.
return knex('event_artist')
.distinct('artist_id')
.join('artist', 'event_artist.artist_id', 'artist.id')
.select('*')
.offset(offset)
.limit(howMany)
This returns duplicate ids, which I don't want. How do I fix this?
You are looking for a query that selects artists rows that have rows in event_artist columns.
In SQL it can be written using exists
select
*
from
artists as a
where
exists (
select
*
from
event_artist as ea
where
ea.artist_id = a.id
)
In knex it can be written
knex('artists as a')
.whereExists(
knex
.select('*')
.from('event_artists as ea')
.whereRaw('ea.artist_id = a.id')
)
this should be left join not just Join-
return knex('event_artist')
.leftJoin('artist', 'event_artist.artist_id', 'artist.id')
.offset(offset)
.limit(howMany)
Related
I am trying to select from one table using the select result from another table. I can run this in two queries but would like to optimize it into just one.
First query.. Select ids where matching other id
select id from lookuptable where paid = '547'
This results in something like this
6316352
6316353
6318409
6318410
6320468
6320469
6320470
6322526
6322527
6324586
6324587
6326648
I would like to then use this result to make another selection. I can do it manually like below. Note, there could be many rows with these values so I've been using a IN statement
select * from "othertable" where id in (6316352,6316353,6318409,6318410,6320468,6320469,6320470,6322526,6322527,6324586,6324587,6326648);
select
ot.*
from
"othertable" as ot
join
lookuptable as lt
on
ot.id = lt.id
where
lt.paid = '547'
The IN operator supports not just value lists but also subqueries, so you can literally write
select * from "othertable" where id in (select id from lookuptable where paid = '547');
I am a frontend developer but I started to write backend stuff. I have spent quite some amount of time trying to figure out how to solve this. I really need some help.
Here are the simplified definitions and relations of two tables:
Relationship between tables
CREATE TABLE IF NOT EXISTS items (
item_id uuid NOT NULL DEFAULT gen_random_uuid() ,
parent_id uuid DEFAULT NULL ,
parent_table parent_tables NOT NULL
);
CREATE TABLE IF NOT EXISTS collections (
collection_id uuid NOT NULL DEFAULT gen_random_uuid() ,
parent_id uuid DEFAULT NULL
);
Our product is an online document collaboration tool, page can have nested pages.
I have a piece of PostgreSQL code for getting all of its ancestor records for given item_ids.
WITH RECURSIVE ancestors AS (
SELECT *
FROM items
WHERE item_id in ( ${itemIds} )
UNION
SELECT i.*
FROM items i
INNER JOIN ancestors a ON a.parent_id = i.item_id
)
SELECT * FROM ancestors
It works fine for nesting regular pages, But if I am going to support nesting collection pages, which means some items' parent_id might refer to "collection" table's collection_id, this code will not work anymore. According to my limited experience, I don't think pure SQL code can solve it. I think writing a PL/pgSQL function might be a solution, but I need to get all ancestor records to given itemIds, which means returning a mix of items and collections records.
So how to return different format of records from a single PL/pgSQL function? I did some research but haven't found any example.
You can make it work by returning a superset as row: comprised of item and collection. One of both will be NULL for each result row.
WITH RECURSIVE ancestors AS (
SELECT 0 AS lvl, i.parent_id, i.parent_table, i AS _item, NULL::collections AS _coll
FROM items i
WHERE item_id IN ( ${itemIds} )
UNION ALL -- !
SELECT lvl + 1, COALESCE(i.parent_id, c.parent_id), COALESCE(i.parent_table, 'i'), i, c
FROM ancestors a
LEFT JOIN items i ON a.parent_table = 'i' AND i.item_id = a.parent_id
LEFT JOIN collections c ON a.parent_table = 'c' AND c.collection_id = a.parent_id
WHERE a.parent_id IS NOT NULL
)
SELECT lvl, _item, _coll
FROM ancestors
-- ORDER BY ?
db<>fiddle here
UNION ALL, not UNION.
Assuming a collection's parent is always an item, while an item can go either way.
We need LEFT JOIN on both potential parent tables to stay in the race.
I added an optional lvl to keep track of the level of hierarchy.
About decomposing row types:
Combine postgres function with query
Record returned from function has columns concatenated
I just can't figure it out why this query work
SELECT id, name, organization_id
FROM facilities
WHERE organization_id = ANY(
'{abc-xyz-123,678-ght-nmp}'
)
But this query wont work with error operator does not exist: uuid = uuid[]
SELECT id, name, organization_id
FROM facilities
WHERE organization_id = ANY(
SELECT organization_ids
FROM admins
WHERE id = 'jkl-iop-345'
)
When the subquery
SELECT organization_ids
FROM admins
WHERE id = 'jkl-iop-345'
give the exact result of {abc-xyz-123,678-ght-nmp}.
I'm using postgres (PostgreSQL) 13.3
The subquery produces one row that contains an array.
If you use = ANY (SELECT ...), the result set is converted to an array, so you end up with
{{abc-xyz-123,678-ght-nmp}}
which is an array of arrays.
You probably want
SELECT id, name, organization_id
FROM facilities
WHERE EXISTS (SELECT 1 FROM admins
WHERE admins.id = 'jkl-iop-345'
AND facilities.organization_id = ANY (admins.organization_ids)
);
Let me remark that storing references to other tables in an array, JSON or other composite data type is an exceptionally bad idea. A normalized schema with a junction table would serve you better.
I need some help. I'm trying to copy a tsql query result into another table. I was able to do it with the below tsql but I need to put some sort of check method to not copy a record if it already exist in the "PageControls" table.
INSERT INTO PageControls (UserId, PageId)
SELECT t1.UserId, t2.PageId FROM
aspnet_users t1, Pages t2
How can I accomplish this?
Thank you.
It looks like you're trying to populate the pagecontrols table with a cartesian product of users and pages. Assuming that's your goal, then you can add not exists to your query to exclude those already in the pagecontrols table:
INSERT INTO PageControls (UserId, PageId)
SELECT t1.UserId, t2.PageId
FROM aspnet_users t1, Pages t2
WHERE NOT EXISTS (
SELECT *
FROM PageControls p
WHERE p.userid = t1.userid and p.pageid = t2.pageid
)
SQL Fiddle Demo
I know this is an often asked question, but I've tried to resolve this myself and could not.
I've got 2 tables to join and now it's returning a duplicate value from the right table.
select am.Journal
,am.EntryNumber
,am.PayInvoice
,am.PayDiscAllowed
,am.PayTaxAmtDisc
,am.PayGrossPayment
,tm.*
from CshJnlPay am right join
(select
Invoice
,SUM(NetSalesValue) as NetSalesValue
,SUM(DiscValue) as DiscValue
,SUM(TaxValue) as TaxValue
,SUM(QtyInvoiced) as QtyInvoiced
from Salesdetail
group by Invoice) tm
on am.PayInvoice = tm.Invoice
where Invoice = 'C90831'
If the query returns 2 rows with the same data from the right table then you have 2 rows in the left table with the same invoice number...
You should check the left table with this query
Select * from CshJnlPay where PayInvoice = 'C90831'
You should get two rows.