I need to select all categories with count of its sub-categories.
Assume here are my tables:
categories
id | title
----------
1 | colors
2 | animals
3 | plants
sub_categories
id | category_id | title | confirmed
------------------------------------
1 1 red 1
2 1 blue 1
3 1 pink 1
4 2 cat 1
5 2 tiger 0
6 2 lion 0
What I want is :
id | title | count
------------------
1 colors 3
2 animals 1
3 plants 0
What I have tried so far:
SELECT c.id, c.title, count(s.category_id) as count from categories c
LEFT JOIN sub_categories s on c.id = s.category_id
WHERE c.confirmed = 't' AND s.confirmed='t'
GROUP BY c.id, c.title
ORDER BY count DESC
The only problem with this query is that this query does not show categories with 0 sub categories!
You also can check that on SqlFiddle
Any help would be great appreciated.
The reason you don't get rows with zero counts is that WHERE clause checks s.confirmed to be t, thus eliminating rows with NULLs from the outer join result.
Move s.confirmed check into join expression to fix this problem:
SELECT c.id, c.title, count(s.category_id) as count from categories c
LEFT JOIN sub_categories s on c.id = s.category_id AND s.confirmed='t'
WHERE c.confirmed = 't'
GROUP BY c.id, c.title
ORDER BY count DESC
Adding Sql Fiddle: http://sqlfiddle.com/#!17/83add/13
I think you can try this too (it evidence what column(s) you are really grouping by):
SELECT c.id, c.title, RC
from categories c
LEFT JOIN (SELECT category_id, COUNT(*) AS RC
FROM sub_categories
WHERE confirmed= 't'
GROUP BY category_id) s on c.id = s.category_id
WHERE c.confirmed = 't'
ORDER BY RC DESC
Related
I have 2 tables:
categories
id | name | | slug | path | parent_id | depth
1 name1 slug1 {1} null 0
2 name2 slug2 {1,2} 1 1
3 name3 slug3 {1,2,3} 2 2
5 nam5 slug5 {5} null 0
......
9 nam4 slug9 {5,9} 5 1
where path is an int[]array type and works like a breadcrumb
items
id | name
1 name1
Between Item and Category there is a M2M relation
item_categories
id | item_id | category_id
1 1 | 3
2 1 9
In the example above the Item is in 3 categories:
I use the following SQL:
SELECT c1.id, c1.name, c1.slug, c1.parent_id FROM categories AS c1
WHERE ARRAY[c1.id] <# (SELECT c2.path FROM categories AS c2 WHERE c2.id=
(SELECT category_id FROM item_categories WHERE item_id=8 LIMIT 1)) order by depth
to extract a breadcrumb base on path and it works.
But I want to get all breadcrumbs(not just one). Removing LIMIT 1 and changing = to in I will have an array of arrays, instead of just an array, and will trigger an error:
more than one row returned by a subquery used as an expression
which is normal.
Example of what I want - Item in:
cat1 - > cat2 - >cat3
ca5 -> cat9
, and from database(so I can loop over them):
[ [{'name':cat1, 'slug':slug1}, {'name':cat2, 'slug':slug2}, {'name':cat3, 'slug':slug3}], [{'name':cat5, 'slug':slug5}, {'name':cat9, 'slug':slug9}]]
dbfiddle: https://dbfiddle.uk/?rdbms=postgres_10&fiddle=f756cfe568d38425dfe25cfec60b1b3f
So instead of obtaining one breadcrumb how can I get an array o breadcrumbs as result ?
using json_build_object, unnest and ordered json_agg:
select
c.id,
json_agg(
json_build_object('name',c2.name,'slug',c2.slug)
order by p.depth
)
from categories as c
inner join lateral unnest(c.path) with ordinality as p(id, depth) on true
inner join categories as c2 on
c2.id = p.id
where
exists (
select *
from item_categories as tt
where
tt.item_id = 1 and
tt.category_id = c.id
)
group by
c.id
db<>fiddle demo
Or you can use depth column from you table if you want:
select
c.id,
json_agg(
json_build_object('name',c2.name,'slug',c2.slug)
order by c2.depth
)
from categories as c
inner join categories as c2 on
c2.id = any(c.path)
where
exists (
select *
from item_categories as tt
where
tt.item_id = 1 and
tt.category_id = c.id
)
group by
c.id
db<>fiddle demo
What I don't like about json_build_object is that you have to name your columns explicitly doing double work, so I've tried to useto_json instead. It works, but honestly, I'm not that familiar with this syntax when alias of the table is passed to the function as an argument (see Using Composite Types in Queries) and could not make it work without lateral join:
select
c.id,
json_agg(to_json(d) order by c2.depth)
from categories as c
inner join categories as c2 on
c2.id = any(c.path)
cross join lateral (select c.name, c.slug) as d
where
exists (
select *
from item_categories as tt
where
tt.item_id = 1 and
tt.category_id = c.id
)
group by
c.id
db<>fiddle demo
Table: ProductionOrder
Id Ordernumber Lotsize
1 Order1 50
2 Order 2 75
3 WO-order1 1
4 WO-order2 1
Table: history
Id ProductionOrderID Completed
1 3 1
2 3 1
3 4 1
4 4 1
Table: ProductionOrderDetail
ID ProductionOrderID ProductionOrderDetailDefID Content
1 1 16 50
2 1 17 7-1-2018
3 2 16 75
4 2 17 7-6-2018
Start of my code:
Select p.ID, p.OrderNumber,
Case productionOrderDetailDefID
Where(Select pd1.productionOrderDetailDefID where ProductionOrderDetialDefID = 16) then min(pd1.content)
from ProductionOrder p
Left join History h1 on p.id = h1.productionOrderID
Left Join ProductionOrderDetail pd1 on p.ID = ProductionOrderID
The result in trying to get is
Id Ordernumber Lotsize Productionorder Completed
1 Order1 50 WO-order1 2
2 Order 2 75 WO-order2 2
Any help would be appreciated.
Try this
SELECT ordernumber,lotsize,Ordernumber,count(Ordernumberid)
FROM productionorder inner join history on productionorder.id = history.Ordernumberid
GROUP BY Ordernumber;
A bit of weird joins going on here. You should add this to a SQL fiddle so that we can see our work easier.
A link to SQL fiddle: http://sqlfiddle.com/
Here is my first attempt
SELECT
po.id
, po.ordernumber
, po.lotsize
, po2.productionorder
, SUM(h.completed)
FROM productionorder as po
INNER JOIN history as h
ON h.id = po.id
INNER JOIN prodcuctionorder as po2
ON po2.ordernumberid = h.ordernumberid
WHERE po.id NOT EXISTS IN ( SELECT ordernumberid FROM history )
GROUP BY
po.id
, po.ordernumber
, po.lotzise
, po2.productionorder
How far does that get you?
I have the following relations:
A Product have multiple Images
A Product can have multiple Categories
A Category can have multiple Products
I want to get:
only the 'short_name' from the first category
only the first image url order_by another parameter
I have the following SQL, in PostgreSql:
SELECT DISTINCT ON(I.product_id) P.id, P.name, P.short_description,
CAT.short_name AS category, I.url
FROM products_product AS P
LEFT JOIN products_product_categories AS RPC ON P.id = RPC.product_id
LEFT JOIN categories_category AS CAT ON RPC.category_id = CAT.id
LEFT JOIN products_productimage AS I ON I.product_id = P.id
WHERE (P.is_active = TRUE)
My issue is that I don't know to limit left join and order by, I try to add LIMIT 1
LEFT JOIN categories_category AS CAT ON RPC.category_id = CAT.id LIMIT 1
but it is not working, I receive a code error 'syntax error at or near "LEFT"'
Category table
id | category_name | category_short_name
1 catA A
2 catB B
3 catC C
Product table
id | product_name | product_desc
1 P1 lorem1
2 P2 lorem2
3 P3 lorem3
ManytoMany: product_category
id product_id category_id
1 1 1
2 2 1
3 1 2
4 3 3
5 3 3
Image table
id url product_id order
1 lo1 1 4
2 lo2 1 0
3 lo3 1 1
4 lo4 2 0
For Product with id1 I expect to get:
name: P1, desc 'lorem1', category short_name : cat A, image url lo2
DISTINCT ON makes no sense without ORDER BY. As you want two different orders (on i.order for images and on cat.id for categories), you must do this in separate subqueries.
select p.id, p.name, p.short_description, c.short_name, i.url
from products_product p
left join
(
select distinct on (pcat.product_id) pcat.product_id, cat.short_name
from products_product_categories pcat
join categories_category cat on cat.id = pcat.category_id
order by pcat.product_id, cat.id
) c on c.product_id = p.id
left join
(
select distinct on (product_id) product_id, url
from products_productimage
order by product_id, order
) i on i.product_id = p.id
where p.is_active
order by p.id;
Two alternatives to write this query are:
subqueries with fetch first row only in the select clause
lateral left joins on subqueries with fetch first row only
Firstly, I'd like to apologise for the ambiguous title (I promise to revise it once I'm actually aware of the problem I'm trying to solve!)
I have two tables, player and match, which look like the following:
player:
id name
-- ----
1 John
2 James
3 April
4 Jane
5 Katherine
match:
id winner loser
-- ------ -----
1 1 2
2 3 4
Records in the match table represent a match between two players, where the id column is generated by the database, and the values in the winner and loser columns reference the id column in the player table.
I want to run a query which spits out the following:
player.id player.name total_wins total_matches
--------- ----------- ---------- -------------
1 John 1 1
2 James 0 1
3 April 1 1
4 Jane 0 1
5 Katherine 0 0
I currently have a query which retrieves total_wins, but I'm not sure how to get the total_matches count on top of that.
select p.id, p.name, count(m.winner)
from player p left join match m on p.id = m.winner
group by p.id, p.name;
Thanks for your help!
Try
select p.id, p.name,
sum(case when m.winner = p.id then 1 end ) as total_wins,
count(m.id) as total_matches
from player p
left join match m on p.id in ( m.winner, m.loser )
group by p.id, p.name;
One method splits the match match table, so you have a single row for each win and loss. The rest is just a left join and aggregation:
select p.id, p.name, coalesce(sum(win), 0) as win, count(m.id) as total_matches
from player p left join
(select match, winner as id, 1 as win, 0 as loss from match
union all
select match, loser as id, 0 as win, 1 as loss from match
) m
on p.id = m.id
group by p.id, p.name;
OK, I'm an absolute beginner in SQL and I got one task to solve and I'm stuck, so I need help on your ideas how to get the required results.
I have 2 tables - first one is PARENTS, with the following data:
ID Name Age
1 John 25
2 Peter 28
3 Anny 30
4 Jack 32
and the second table is CHILDRENS, with the following data:
children_id parent_id name age
1 1 mary 5
2 1 Susanne 4
3 2 stephen 12
4 4 Kevin 7
What SQL command can be used to get following result:
id parent name number of childrens
1 John 2
2 Peter 1
3 Anny 0
4 Jack 1
Thanks in advance!
Try like this
select PARENTS.id,PARENTS.name,count(CHILDRENS.name)
from PARENTS left join CHILDRENS on PARENTS.id=CHILDRENS.parent_id
group by PARENTS.id,PARENTS.name
As mentioned by Jarlh in comments, Use LEFT OUTER JOIN + Group by
SELECT p.id,
p.name,
Count(parent_id) as number_of_childrens
FROM PARENTS p
LEFT OUTER JOIN CHILDRENS c
ON c.parent_id = p.ID
Group by p.id,
p.name
select p.id, p.name, count(p.id) as number_of_childrens
from parents p
left join childrens c
on p.parent_id = c.parent_id
group by p.id, p.name
SELECT A.ID
, A.name AS parent_name
, COUNT(B.children_id) AS number_of_children
FROM PARENTS AS A
LEFT JOIN CHILDRENS AS B
ON A.ID = B.parent_id
GROUP BY A.ID
, A.name
A left join, count and group by.