I have a table, with columns
product_id, status, for example:
product_id
status
1
ok
2
bad
1
ok
3
bad
2
bad
1
ok
I'd like to show count of all possible combinations of product_ID and status:
product_id
status
count
1
ok
3
1
bad
0
2
ok
0
2
bad
2
3
ok
0
3
bad
1
The solution I've found is that I could use a Cartesian join and then union it with regular counts and aggregate the results (works fine):
SELECT product_id, status, SUM(cnt) FROM (
---all combinations, no count
SELECT DISTINCT t1.product_id, t2.status, 0 AS cnt
FROM
details t1,
details t2
UNION
---counts of existing combinations
SELECT DISTINCT product_id, status, COUNT(status) AS cnt
FROM details
GROUP BY product_id, status) AS T1
GROUP BY product_id, status
Now I am wondering, is here a better way to do it?
I learning SQL with PostgreSQL and Access SQL. Comments are added to clarify (left-out in Access code).
Use CROSS JOIN to build all combinations and top up with a LEFT JOIN:
SELECT p.product_id, s.status, COUNT(t.any_not_null_column)
FROM (SELECT DISTINCT product_id FROM t) AS p
CROSS JOIN (SELECT DISTINCT status FROM t) AS s
LEFT JOIN t ON p.product_id = t.product_id AND s.status = t.status
GROUP BY p.product_id, s.status
The following is a Postgres solution (a database I strongly recommend over MS Access). The idea is to generate all the rows and then use left join and group by to get the counts you want:
select p.product_id, s.status, count(d.product_id)
from (select distinct product_id from details) p cross join
(values ('ok'), ('bad')) s left join
details d
on d.product_id = p.product_id and d.status = s.status
group by p.product_id, s.status;
Note: You might have other tables that have the list of products and/or statuses that you want.
An equivalent version in MS Access (which would also work in Postgres) might look like:
select p.product_id, s.status, count(d.product_id)
from ((select distinct product_id from details) p,
(select distinct status from details) s
) left join
details d
on d.product_id = p.product_id and
d.status = s.status
group by p.product_id, s.status;
Related
I have Database table and trying to write query to find sold and not sold product list from one table.
Table is Below
Expecting Result
How do i get this result? i am using CTE to create Tamp table and with all services and then do left join but it dose give me only product sold in Feb, but i want all product with no sell too.
You can cross join the products and the dates, and then bring the table with a left join:
select
p.product,
t.quantity_sold,
d.yr,
d.mn
from (select distinct product from mytable) p
cross join (select distinct yr, mn from mytable) d
left join mytable t
on t.product = p.product
and t.yr = d.yr
and t.mn = d.mn
This puts nulls for rows with no sale - that's presumably a numeric column so you generally don't want to write a string like 'Not Sold' into it.
If there is a possibility of duplicate (product, yr, mn), you might want to use outer aggregation:
select
p.product,
sum(t.quantity_sold) quantity_sold,
d.yr,
d.mn
from (select distinct product from mytable) p
cross join (select distinct yr, mn from mytable) d
left join mytable t
on t.product = p.product
and t.yr = d.yr
and t.mn = d.mn
group by p.product, d.yr, d.mn
I have two tables: products and postings. A product is a consumer product (ex. iPhone X), and a posting is a listing for a product on an online marketplace (ex. eBay posting). A single product has zero or more associated postings.
Is there any way to select only postings which have a "sibling"? ie. Select all postings whose product column is equal to any other postings' product column.
SELECT * FROM postings a
INNER JOIN products b ON a.product = b.id
WHERE COUNT(b) > 0
I am wondering your inner join should only do the trick, but in case I am missing something you can try this
With a as
(
SELECT a.*,b.*, count(*) over(Partition by b.id) cnt
FROM postings a
INNER JOIN products b ON a.product = b.id
)
Select * from a where cnt > 0
If you just want postings, then I would suggest:
select p.*
from postings p
where exists (select 1
from postings p2
where p2.product = p.product and
p2.posting_id <> p.posting_id
);
Or, use window functions like this:
select p.*
from (select p.*,
count(*) over (partition by p.product) as cnt
from postings p
) p
where cnt > 1;
Note that these do not require the products table, because the product information is available in postings.
I have problems with some query. I need to get max value and product_name from that query:
select
products.product_name,
sum(product_invoice.product_amount) as total_amount
from
product_invoice
inner join
products on product_invoice.product_id = products.product_id
inner join
invoices on product_invoice.invoice_id = invoices.invoice_id
where
month(invoices.invoice_date) = 2
group by
products.product_name
This query returns a result like this:
product_name | total_amount
--------------+--------------
chairs | 70
ladders | 500
tables | 150
How to get from this: ladders 500?
Select product_name,max(total_amount) from(
select
products.product_name,
sum(product_invoice.product_amount) as total_amount
from product_invoice
inner join products
on product_invoice.product_id = products.product_id
inner join invoices
on product_invoice.invoice_id = invoices.invoice_id
where month(invoices.invoice_date) = 2
group by products.product_name
) outputTable
You can use order by and fetch first 1 row only:
select p.product_name,
sum(pi.product_amount) as total_amount
from product_invoice pi inner join
products p
on pi.product_id = p.product_id inner join
invoices i
on pi.invoice_id = i.invoice_id
where month(i.invoice_date) = 2 -- shouldn't you have the year here too?
group by p.product_name
order by total_amount
fetch first 1 row only;
Not all databases support the ANSI-standard fetch first clause. You may need to use limit, select top, or some other construct.
Note that I have also introduced table aliases -- they make the query easier to write and to read. Also, if you are selecting the month, shouldn't you also be selecting the year?
In older versions of SQL Server, you would use select top 1:
select top (1) p.product_name,
sum(pi.product_amount) as total_amount
from product_invoice pi inner join
products p
on pi.product_id = p.product_id inner join
invoices i
on pi.invoice_id = i.invoice_id
where month(i.invoice_date) = 2 -- shouldn't you have the year here too?
group by p.product_name
order by total_amount;
To get all rows with the top amount, use SELECT TOP (1) WITH TIES . . ..
If you are using SQL Server, then TOP can offer a solution:
SELECT TOP 1
p.product_name,
SUM(pi.product_amount) AS total_amount
FROM product_invoice pi
INNER JOIN products p
ON pi.product_id = p.product_id
INNER JOIN invoices i
ON pi.invoice_id = i.invoice_id
WHERE
MONTH(i.invoice_date) = 2
GROUP BY
p.product_name
ORDER BY
SUM(pi.product_amount) DESC;
Note: If there could be more than one product tied for the top amount, and you want all ties, then use TOP 1 WITH TIES, e.g.
SELECT TOP 1 WITH TIES
... (the same query I have above)
Suppose I have these three tables:
I want to get, for all products, it's product_id and the client that bougth it most times (the biggest client of the product).
I solved it like this:
SELECT
product_id AS product,
(SELECT TOP 1 client_id FROM Bill_Item, Bill
WHERE Bill_Item.product_id = p.product_id
and Bill_Item.bill_id = Bill.bill_id
GROUP BY
client_id
ORDER BY
COUNT(*) DESC
) AS client
FROM Product p
Do you know a better way?
the inner query will give you the ranking. The outer query will give you the client that puchase the most for a product
SELECT *
(
SELECT i.product_id, b.client_id,
r = row_number() over (partition by i.product_id
order by count(*) desc)
FROM Bill b
INNER JOIN Bill_Item i ON b.bill_id = i.bill_id
GROUP BY i.product_id, b.client_id
) d
WHERE r = 1
I was going to submit pretty much the same thing as #Squirrell only with a Common Table Expression [CTE] rather than a derived table. So I wont duplicate that but there are some learning points concerning your query. First is IMPLICIT JOINS such as FROM Bill_Item, Bill are really easy to have uintended consequences (one of many questions: Queries that implicit SQL joins can't do?) Next for the Calculated column you can actually do this in a OUTER APPLY or CROSS APPLY which is a very useful technique.
So you could re-write your method as follows:
SELECT *
FROM
Product p
OUTER APPLY (SELECT TOP 1 b.client_id
FROM
Bill_Item bi
INNER JOIN Bill b
ON bi.bill_id = b.bill_id
WHERE
bi.product_id = p.product_id
GROUP BY
b.client_id
ORDER BY
COUNT(*) DESC) c
And to show you how squirell's answer can still include products that have never been sold all you need to do is join Products and LEFT JOIN to other tables:
;WITH cte AS (
SELECT
p.product_id
,b.client_id
,ROW_NUMBER() OVER (PARTITION BY p.product_id ORDER BY COUNT(*) DESC) as RowNumber
FROM
Product p
LEFT JOIN Bill_Item bi
ON p.product_id = bi.product_id
LEFT JOIN Bill b
ON bi.bill_id = b.bill_id
GROUP BY
p.product_id
,b.client_id
)
SELECT *
FROM
cte
WHERE
RowNumber = 1
Techniques used in some of these that are useful.
CTE
APPLY (Outer & Cross)
Window Functions
Squirrel's answer doesn't return products that have never been sold. If you want to include those, then your approach is ok, although I would write the query as:
SELECT product_id as product,
(SELECT TOP 1 b.client_id
FROM Bill_Item bi JOIN
Bill b
ON bi.bill_id = b.bill_id
WHERE Bill_Item.product_id = p.product_id
GROUP BY client_id
ORDER BY COUNT(*) DESC
) as client
FROM Product p;
You can also express this using APPLY, but a correlated subquery is also fine.
Note the correct use of the explicit JOIN syntax.
I have the following SQL command:
SELECT * from products
WHERE id IN (
SELECT product_id, count(*)
FROM account_products
GROUP BY product_id
)
obviously it doesnt retrieve any data, because the internal query retrieves two columns (product_id and count).
But I need the count too, because I'm gonna use it to make some math later.
How can I use this IN query using the count(*) too?
Thanks!
Join them:
select products.*, t.product_count
from products
join (
SELECT product_id, count(*) as product_count
FROM account_products
GROUP BY product_id
) as t on t.product_id = products.id
select products.*, count( account_products.product_id)
from products join account_products on
products.product_id = products.id
group by products.* (obviously all products-fields)
Or with a subquery in the select clause, when your DBMS supports it:
SELECT
products.*,
(SELECT count(*) FROM account_products ap WHERE ap.product_id = products.id) as "Number of Accounts"
from products
This might work for you:
WITH MyAccountProducts AS
(
SELECT product_id, count(*) AS CountOfAccountProducts
FROM account_products
GROUP BY product_id
)
SELECT p.*,ap.CountOfAccountProducts
from products AS p
INNER JOIN MyAccountProducts AS ap ON p.id=ap.product_id