I have a bunch of rows(fruits) in a table, along with the basic details like fruit name, description color.
I want to know how many people viewed that product, how people liked it, etc...
This is what I tried but it is returning completely wrong numbers:
SELECT
vw.[Id],
vw.[Name],
vw.[Color],
-- This is returning 268 for id 1 but it supposed to be 134
(COUNT(v.PublicImageViewId) OVER (PARTITION BY v.[publicImageId] )) AS [ViewCount],
-- This is returning 268 for id 1 but it supposed to be 2, both these counts are same and wrong
(COUNT(u.PublicImageUpvoteId) OVER (PARTITION BY v.[publicImageId] )) AS [UpvoteCount]
FROM
[PublicImage] vw
LEFT JOIN
[PublicImageUpvote] u ON u.[PublicImageId] = vw.[PublicImageId]
LEFT JOIN
[PublicImageFavourite] f ON f.[PublicImageId] = vw.[PublicImageId]
LEFT JOIN
[PublicImageView] v ON v.PublicImageId = vw.[PublicImageId]
This might not be done like this or I'm doing blunder mistake.
All I wanted is for each product no of views, no of likes, no of favorites ...etc
Tables:
Public Image Table
PublicImageId: PK
name, color
PublicImageUpvote (same for PublicImageView, PublicImageFavourite)
PublicImageUpvoteId: PK
PublicImageId: FK
CreatedBy, Created Date
You must GROUP BY vw.[Id], vw.[Name], vw.[Color] and count the distinct values:
SELECT
vw.[Id],
vw.[Name],
vw.[Color],
COUNT(DISTINCT v.PublicImageViewId) AS [ViewCount],
COUNT(DISTINCT u.PublicImageUpvoteId) AS [UpvoteCount]
FROM [PublicImage] vw
LEFT JOIN [PublicImageUpvote] u ON u.[PublicImageId] = vw.[PublicImageId]
LEFT JOIN [PublicImageFavourite] f ON f.[PublicImageId] = vw.[PublicImageId]
LEFT JOIN [PublicImageView] v ON v.PublicImageId = vw.[PublicImageId]
GROUP BY vw.[Id], vw.[Name], vw.[Color]
May I suggest that you need another table for this
How many people viewed that product, how people liked it, etc...
Then use JOIN
Related
I need to write SQL query like:
Show all countries with more than 1000 users, sorted by user count.
The country with the most users should be at the top.
I have tables:
● Table users (id, email, citizenship_country_id)
● Table countries (id, name, iso)
Users with columns: id, email, citizenship_country_id
Countries with columns: id, name, iso
SELECT countries.name,
Count(users.citiizenship_country_id) AS W1
FROM countries
LEFT JOIN users ON countries.id = users.citizenship_country_id
GROUP BY users.citiizenship_country_id, countries.name
HAVING ((([users].[citiizenship_country_id])>2));
But this does not work - I get an empty result set.
Could you please tell me what I'm doing wrong?
A LEFT JOIN is superfluous for this purpose. To have 1000 users, you need at least one match:
SELECT c.name, Count(*) AS W1
FROM countries c JOIN
users u
ON c.id = u.citizenship_country_id
GROUP BY c.name
HAVING COUNT(*) > 1000;
Notice that table aliases also make the query easier to write and to read.
Group by country name and use HAVING Count(u.citiizenship_country_id)>1000, it filters rows after aggregation:
SELECT c.name,
Count(u.citiizenship_country_id) AS W1
FROM countries c
INNER JOIN users u ON c.id = u.citizenship_country_id
GROUP BY c.name
HAVING Count(u.citiizenship_country_id)>1000
ORDER BY W1 desc --Order top counts first
;
As #GordonLinoff pointed, you can use INNER JOIN instead of LEFT JOIN, because anyway this query does not return counries without users and INNER JOIN performs better because no need to pass not joined records to the aggregation.
I have these 3 tables:
Areas - id, name
Persons - id, area_id
Special_Persons - id_person, date
I'd like to produce a list of all Areas, followed by a count of Special Persons in each area, including Areas with no Special Persons.
If I do a left join of Areas and Persons, like this:
select a.id as idArea, count(p.id) as count
from areas a
left join persons p on p.area_id = a.id
group by a.id;
This works just fine; Areas that have no Persons show up, and have a count of 0.
What I am not clear on is how to do the same thing with the special_persons table, which currently only has 2 entries, both in the same Area.
I have tried the following:
select a.id as idArea, count(sp.id_person) as count
from special_persons sp, areas a
left join persons p on p.area_id = a.id
where p.area_id = a.id
and sp.id_person = p.id
group by a.id;
And it only returns 1 row, with the Area that happens to have 2 Special Persons in it, and a count of 2.
To continue getting a list of all areas, do I need to use a sub-query? Another join? I'm not sure how to go about it.
You can add another left join to the Special_Persons table:
select a.id as idArea, count(p.id), count(sp.id_person)
from areas a
left join persons p on p.area_id = a.id
left join special_persons sp on sp.id_person = p.id
group by a.id;
I'm new to postgresql. I have a database that has three tables in it: Users, Order, Comments. Those three tables look like this
Orders Comments
------ --------
ID ID
UserID UserID
Description Details
CreatedOn CreatedOn
I'm trying to get a list of all of my users and how many orders each user has made and how many comments each user has made. In other words, the result of the query should look like this:
UserID Orders Comments
------ ------ --------
1 5 7
2 2 9
3 0 0
...
Currently, I'm trying the following:
SELECT
UserID,
(SELECT COUNT(ID) FROM Orders WHERE UserID=ID) AS Orders,
(SELECT COUNT(ID) FROM Comments WHERE UserID=ID) AS Comments
FROM
Orders o,
Comments c
WHERE
o.UserID = c.UserID
Is this the right way to do this type of query? Or can someone provide a better approach from a performance standpoint?
SQL Fiddle
select
id, name,
coalesce(orders, 0) as orders,
coalesce(comments, 0) as comments
from
users u
left join
(
select userid as id, count(*) as orders
from orders
group by userid
) o using (id)
left join
(
select userid as id, count(*) as comments
from comments
group by userid
) c using (id)
order by name
The usual way to do this is by using outer joins to the two other tables and then group by the id (and name)
select u.id,
u.name,
count(distinct o.id) as num_orders,
count(distinct c.id) as num_comments
from users u
left join orders o on o.userId = u.id
left join comments c on c.userId = u.id
group by u.id, u.name
order by u.name;
That might very well be faster than your approach. But Postgres' query optimizer is quite smart and I have seen situations where both solutions are essentially equal in performance.
You will need to test that on your data and also have a look at the execution plans in order to find out which one is more efficient.
Basically, what I want to do is join 4 tables together and return 1 row for each boat.
Table Layouts
[Boats]
id, date, section, raft
[Photos]
id, boatid, pthurl, purl
[River_Company]
id, sort, company, company_short
[River_Section]
id, section
Its very simple as far as structure, however, I've having the time of my life trying to get it to return only 1 row. No boat will ever be on the same day, the only thing that's messing this up is the photo table.
If you know a better way for it to return the record table for all the boats boats and only 1 photo from the photo table, please, please post it!!
Desired Format
boats.id, boats.date, river_company.company, river_section.section, photos.purl, photos.pthurl
It's basically how joins work. Since boats and photos are in one-to-many relationships and you want one-to-one-like query, you need to explicitly express it with predicate. For example:
select b.*
from
boats b
inner join photos p
on b.id = p.boatid
where p.id = (select max(id) from photos where boatid = b.id)
Assuming your ID column is the relation that you have designed:
SELECT Boats.* FROM Boats
LEFT OUTER JOIN Photos on Photos.ID =
(
SELECT TOP 1 Photos.ID FROM Photos
INNER JOIN Boats ON Photos.BoatID = Boats.ID
)
INNER JOIN River_Company on River_Company.ID = Boats.ID
INNER JOIN River_Section on River_Section.ID = Boats.ID
So basically, this will:
Guarantee the maximum row count of 1. (It's a bit dirty, but fact is if you have more than one photo, more than one link will be returned otherwise)
If there are no photo's, the boat will still be returned
I have four tables: Customer, CustomerCategory, Limit, and LimitCategory. A customer can be in multiple categories and a limit can also have multiple categories. I need to write a query that will return the customer name and limit amount where ALL the customers categories match ALL the limit categories.
I'm guessing it would be similar to the answer here, but I can't seem to get it right. Thanks!
Edit - Here's what the tables look like:
tblCustomer
customerId
name
tblCustomerCategory
customerId
categoryId
tblLimit
limitId
limit
tblLimitCategory
limitId
categoryId
I THINK you're looking for:
SELECT *
FROM CustomerCategory
LEFT OUTER JOIN Customer
ON CustomerCategory.CustomerId = Customer.Id
INNER JOIN LimitCategory
ON CustomerCategory.CategoryId = LimitCategory.CategoryId
LEFT OUTER JOIN Limit
ON Limit.Id = LimitCategory.LimitId
Updated!
Thanks to Felix for pointing out a flaw in my existing solution (3 years after I originally posted it, hehe). After looking at it again, I think this might be correct. Here I'm getting (1) the customers and limits with matching categories, plus the number of matching categories, (2) the number of categories per customer, (3) the number of categories per limit, (4) I then ensure the number of categories for customer and limits is the same as the number of the matches between the customers and limits:
UNTESTED!
select
matches.name,
matches.limit
from (
select
c.name,
c.customerId,
l.limit,
l.limitId,
count(*) over(partition by cc.customerId, lc.limitId) as matchCount
from tblCustomer c
join tblCustomerCategory cc on c.customerId = cc.customerId
join tblLimitCategory lc on cc.categoryId = lc.categoryId
join tblLimit l on lc.limitId = l.limitId
) as matches
join (
select
cc.customerId,
count(*) as categoryCount
from tblCustomerCategory cc
group by cc.customerId
) as customerCategories
on matches.customerId = customerCategories.customerId
join (
select
lc.limitId,
count(*) as categoryCount
from tblLimitCategory lc
group by lc.limitId
) as limitCategories
on matches.limitId = limitCategories.limitId
where matches.matchCount = customerCategories.categoryCount
and matches.matchCount = limitCategories.categoryCount
I don't know if this will work or not, just a thought i had and i can't test it, I'm sures theres a nicer way! don't be too harsh :)
SELECT
c.customerId
, l.limitId
FROM
tblCustomer c
CROSS JOIN
tblLimit l
WHERE NOT EXISTS
(
SELECT
lc.limitId
FROM
tblLimitCategory lc
WHERE
lc.limitId = l.id
EXCEPT
SELECT
cc.categoryId
FROM
tblCustomerCategory cc
WHERE
cc.customerId = l.id
)