thanks in advance for any help on this, I am a bit of a newbie to MS SQL and I want to do something that I think is achievable but don't have the know how.
I have a simple table called "suppliers" where I can do (SELECT id, name FROM suppliers ORDER BY id ASC)
id
name
1
ACME
2
First Stop Business Supplies
3
All in One Supply Warehouse
4
Farm First Supplies
I have another table called "products"
id
name
supplier_id
1
Item 1
2
2
Item 2
1
3
Item 3
1
4
Item 4
3
5
Item 5
2
I want to list all the suppliers and get the total amount of products for each supplier if that makes sense on the same row? I am just not sure how to pass the suppliers.id through the query to get the count.
I am hoping to get to this:
id
name
total_products
1
ACME
2
2
First Stop Business Supplies
2
3
All in One Supply Warehouse
1
4
Farm First Supplies
0
I really appreciate any help on this.
Three concepts to grasp here. Left Join, group by, and Count().
select s.id, s.name, Count(*) as total_products
from suppliers s
left join products p on s.id=p.supplier_id --the left join gets your no matches
group by s.id, s.name
left join is a join where all of the values from the first table are kept even if there are no matches in the second.
Group by is an aggregation tool where the columns to be aggregated are entered.
Count() is simply a count of transactions for the grouped columns.
Try this :-
SELECT id, name, C.total_products
FROM Suppliers S
OUTER APPLY (
SELECT Count(id) AS total_products
FROM Products P
WHERE P.supplier_id = S.id
) C
Related
I have a table with student info [STU] and a table with parent info [PAR]. I want to return an email address for each student, but just one. So I run this query:
SELECT [STU].[ID], [PAR].[EM]
FROM (SELECT [STU].* FROM DB1.STU)
STU LEFT JOIN (SELECT [PAR].* FROM DB1.PAR) PAR ON [STU].[ID] = [PAR].[ID]
This gives me the below table:
Student ID ParentEmail
1 jim#email.com
1 sarah#email.com
2 paul#email.com
2 tim#email.com
3 bill#email.com
3 frank#email.com
3 joyce#email.com
4 greg#email.com
5 tony#email.com
5 sam#email.com
Each student has multiple parent emails, but I only want one. In other words, I want the output to look like this:
Student ID ParentEmail
1 jim#email.com
2 paul#email.com
3 frank#email.com
4 greg#email.com
5 sam#email.com
I've tried so many things. I've tried using GROUP BY and MIN/MAX and I've tried complex CASE statements, and I've tried COALESCE but I just can't seem to figure it out.
I think OUTER APPLY is the simplest method:
SELECT [STU].[ID], [PAR].[EM]
FROM DB1.STU OUTER APPLY
(SELECT TOP (1) [PAR].*
FROM DB1.PAR
WHERE [STU].[ID] = [PAR].[ID]
) PAR;
Normally, there would be an ORDER BY in the subquery, to give you control over which email you want -- the longest, shortest, oldest, or whatever. Without an ORDER BY it returns just one email, which is what you are asking for.
If you just want one column from the parent table, a simple approach is a correlated subquery:
select
s.id student_id,
(select max(p.em) from db1.par p where p.id = s.id) parent_email
from db1.stu s
This gives you the greatest parent email per student.
We have a situation in which one part of our stored procedure need to be filled with a join query, which had multiple filters in it. We need a solution only with join (it is easy to implement in the subquery, but our situation demands it to be a join [since the procedure has a where clause followed by it] )
We have two tables Customer and Order. We need to exclude the rows of Customer table, if Customer_id is present Order table & order_code = 10 & Customer.Grade = 3. It is not mandatory for all Customer_id to be present in Order table, but we still need it in the final result.
Customer Table OrderTable
Customer_id Grade Customer_id order_code
1 3 1 10
2 3 1 40
3 2 2 50
4 3 3 30
*Multiple Customer_id can be present in the OrderTable
Expected result :
Customer_id Grade
2 3
3 2
4 3
I think this may be what you need, not sure I understand the question properly.
select c.id, c.grade
from customer c left join customer_order o on (c.id = o.customer_id and o.order_code <> 10)
where c.grade = 3
This should give you all customers with a Grade of 3 that also have orders, provided the order_code is not 10. If you want to show customers that do not have any orders also, make it a left join.
You can express the logic like this:
select c.*
from customers c
where not (grade = 3 and
exists (select 1
from orders o
where o.customer_id = c.customer_id and
o.order_code = 10
)
);
I am trying to write a query in db2 for a database that has books and the customers who bought them and I am to find the pairs of customers who bought common books.
Say for example the DB is called "DB" and it looks like this
CustomerID Book Cost
1 Harry Potter 12
2 SOUE 6
3 Harry Potter 12
4 Harry Potter 12
5 SOUE 6
6 SOUE 6
I am basically trying to get the resulting table look like
Customer1 Customer2
1 3
1 4
2 5
2 6
I have tried using group by's but I cant seem to get the idea right
I've tried
Select book
from DB
group by book
which uniquely gives me all the books but I don't know how I would go about getting the customer pairs. Any help would be greatly appreciated thank you.
I'd self-join according to the book column. In order to avoid conceptual duplicates (e.g., 1-3 and 3-1), you could make an arbitrary decision to always display the lower customer ID on the left:
SELECT DISTINCT a.customerid, b.customerid
FROM mytable a
JOIN mytable b ON a.book = b.book AND a.customerid < b.customerid
EDIT:
To answer the question in the comments, if you want to display customer names instead of ids, you'd need to join the customers table to this query, twice, once for each column:
SELECT DISTINCT ca.name AS customer1, cb.name AS customer2
FROM purchases pa
JOIN purchases pb ON pa.book = pb.book AND pa.customerid < pb.customerid
JOIN customers ca ON pa.customer_id = ca.id
JOIN customers cb ON pb.customer_id = cb.id
I have searched Google and Stack Overflow for a answer to my query, but I feel my lack of SQL vocabulary is standing in my way of finding an answer as I believe this would be a common question. Any helpful points in the direction of what I need to be reading are always welcome.
On to the question, I'm attempting to join three tables in Oracle 8i, for example, a Company Table, an Invoice Table and a Jobs Table there is no link between the Invoice Table and the Jobs Table. I am hoping that in one query I can link all three tables returning all invoices and all jobs for a company without returning all jobs for each invoice (see my example results below).
I want to see:
Company 1 Invoice 1 Job 1
Company 1 Invoice 2 Job 2
Company 1 Invoice 3 Job 3
I don't want to see:
Company 1 Invoice 1 Job 1
Company 1 Invoice 1 Job 2
Company 1 Invoice 1 Job 3
Company 1 Invoice 2 Job 1
Company 1 Invoice 2 Job 2
Company 1 Invoice 2 Job 3
Company 1 Invoice 3 Job 1
Company 1 Invoice 3 Job 2
Company 1 Invoice 3 Job 3
As always thank you for any help you can offer.
EDIT:
Essentially both the Invoice and Job Tables both have a Company Table Key field it's just that the Job and Invoice table have no link to each other directly. If the instance comes up when there are 2 Invoices and 3 Jobs I'd ideally like it to show and vice versa:
Company 1 Invoice 1 Job 1
Company 1 Invoice 2 Job 2
Company 1 Job 3
Although looking at the problem like this makes me feel that this is further away from an easier answer than I hoped.
Your requirement means that you have a problem with your schema. My first advice in this case would be to modify your schema: add a job_id to invoice or an invoice_id to job (or a N-N relationship table invoice_job).
If you're not willing to update your schema, you can work a query that will make the join. The following query will basically join job and invoice one-to-one:
SELECT c.company_id, ij.job_id, ij.invoice_id
FROM company c
LEFT JOIN (SELECT job_id, invoice_id,
NVL(j.company_id, i.company_id) company_id
FROM (SELECT j.job_id, j.company_id,
row_number() OVER (PARTITION BY company_id
ORDER BY job_id) job_no
FROM job j) j
FULL OUTER JOIN
(SELECT i.invoice_id, i.company_id,
row_number() OVER (PARTITION BY company_id
ORDER BY invoice_id) invoice_no
FROM invoice i) i
ON j.company_id = i.company_id
AND j.job_no = i.invoice_no) ij
ON c.company_id = ij.company_id
The join condition here is artificial. If you remove an invoice, the jobs and invoices relationship may change.
If the two tables are really unrelated, you may want instead to display the results differently, for example:
SQL> SELECT cj.company_id, cj.jobs,
2 listagg(i.invoice_id, ',')
3 WITHIN GROUP (ORDER BY i.invoice_id) invoices
4 FROM (SELECT c.company_id,
5 listagg(j.job_id, ',') WITHIN GROUP (ORDER BY job_id) jobs
6 FROM company c LEFT JOIN job j ON c.company_id = j.company_id
7 GROUP BY c.company_id) cj
8 LEFT JOIN invoice i ON cj.company_id = i.company_id
9 GROUP BY cj.company_id, cj.jobs;
COMPANY_ID JOBS INVOICES
----------- ------ --------
1 1,2,3 1,2
My question is quite similar to Restricting a LEFT JOIN, with a variation.
Assuming I have a table SHOP and another table LOCATION. Location is a sort of child table of table SHOP, that has two columns of interest, one is a Division Key (calling it just KEY) and a "SHOP" number. This matches to the Number "NO" in table SHOP.
I tried this left outer join:
SELECT S.NO, L.KEY
FROM SHOP S
LEFT OUTER JOIN LOCATN L ON S.NO = L.SHOP
but I'm getting a lot of duplicates since there are many locations that belong to a single shop. I want to eliminate them and just get a list of "shop, key" entries without duplicates.
The data is correct but duplicates appear as follows:
SHOP KEY
1 XXX
1 XXX
2 YYY
3 ZZZ
3 ZZZ etc.
I would like the data to appear like this instead:
SHOP KEY
1 XXX
2 YYY
3 ZZZ etc.
SHOP table:
NO
1
2
3
LOCATION table:
LOCATION SHOP KEY
L-1 1 XXX
L-2 1 XXX
L-3 2 YYY
L-4 3 YYY
L-5 3 YYY
(ORACLE 10g Database)
You need to GROUP BY 'S.No' & 'L.KEY'
SELECT S.NO, L.KEY
FROM SHOP S
LEFT OUTER JOIN LOCATN L
ON S.NO = L.SHOP
GROUP BY S.NO, L.KEY
EDIT Following the update in your scenario
I think you should be able to do this with a simple sub query (though I haven't tested this against an Oracle database). Something like the following
UPDATE shop s
SET divnkey = (SELECT DISTINCT L.KEY FROM LOCATN L WHERE S.NO = L.SHOP)
The above will raise an error in the event of a shop being associated with locations that are in multiple divisions.
If you just want to ignore this possibility and select an arbitrary one in that event you could use
UPDATE shop s
SET divnkey = (SELECT MAX(L.KEY) FROM LOCATN L WHERE S.NO = L.SHOP)
I had this problem too but I couldn't use GROUP BY to fix it because I was also returning TEXT type fields. (Same goes for using DISTINCT).
This code gave me duplicates:
select mx.*, case isnull(ty.ty_id,0) when 0 then 'N' else 'Y' end as inuse
from master_x mx
left outer join thing_y ty on mx.rpt_id = ty.rpt_id
I fixed it by rewriting it thusly:
select mx.*,
case when exists (select 1 from thing_y ty where mx.rpt_id = ty.rpt_id) then 'Y' else 'N' end as inuse
from master_x mx
As you can see I didn't care about the data within the 2nd table (thing_y), just whether there was greater than zero matches on the rpt_id within it. (FYI: rpt_id was also not the primary key on the 1st table, master_x).