Selecting from table with categories of people - sql

I created a database in ms sql , in the database I have three category of persons namely staff, customers, suppliers whom I stored in different tables create serial unique id for each.
Now these persons id are stored under person_id and a column names person type which stores whether its a staff, custimer or supplier in the transaction table, The problem lies in selecting the records from the transaction table like this pseudo code
Select t.*,s.na as staff,sp.name as supplier, c.name as customer
From Trans t
left join Staff s on s.id = t.pid
left join Suppliers sp on sp.id = t.pid
left join Customers c on c.id = t.pid
This returns one row, instead of at least 3 or more, How do I solve this problem
My trans table
person_id Person_type Trans_id
1 staff 1
1 customer 2
2 customer 3
3 suppler 4
1 staff 5
Expected output
person_name Trans_id
james 1
mark 2
dan 3
jude 4
james 5
Staff, Customers, and suppliers are stored in their different tables

That's what the Join does, combine data from multiple tables into one result row. If you want to "keep the rows", not combine them, you can use UNION
(
Select t.* From Trans t
left join Staff s on s.id = t.pid
)
UNION
(
Select t.* From Trans t
left join Suppliers sp on sp.id = t.pid
)
UNION
(
Select t.* From Trans t
left join Customers c on c.id = t.pid
)
This will get you the multiple rows you want BUT still not sure you have defined it right. I see you are only taking columns from Trans, so you're not getting any data from the other tables. And you're doing left outer joins so the other tables won't affect the selection. So I think it's just that same as selecting from just Trans.
If what you want is data from Trans where there is corresponding entry in the other tables, then do the UNION, but also change the outer joins to inner.

Related

SQL Selecting & Counting In the same query

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

joining a table on 2 fields

I want to pull a person and their supervisor names from a table. The persons table has the supervisor_id and the person_id. The names table has name_id and a Full Name field. If I join Person ON either supervisor_id or person_id, how do I get the other to display as well?
You need to join twice, one for each relationship you have:
SELECT
-- Persons' columns
P.*,
-- Superviser name columns
SN.*,
-- Person name columns
PN.*
FROM
persons AS P
LEFT JOIN names AS SN ON P.supervisor_id = SN.name_id
LEFT JOIN names AS PN ON P.person_id = PN.name_id
Or you can join with an OR clause, but you won't be able to know which record did you join with unless you check with a CASE.
SELECT
-- Persons' columns
P.*,
-- name columns
N.*,
IsSupervisor = CASE WHEN P.supervisor_id = N.name_id THEN 'Yes' ELSE 'No' END
FROM
persons AS P
LEFT JOIN names AS N ON
P.supervisor_id = N.name_id OR
P.person_id = N.name_id
This last approach will display 2 rows as it will match either one or the other on different occasions, not both with the same persons row (as the first example).
A (self)join is what you need:
select p.*, supervisor=ps.name
from Person p join person ps on p.supervisor_id=ps.id

Two group by tables stich another table

I have 3 tables I need to put together.
The first table is my main transaction table where I need to get distinct transaction id numbers and company id. It has all the important keys. The transaction ids are not unique.
The second table has item info which is linked to transaction id numbers which are not unique and I need to pull items.
The third table has company info which has company id.
Now I've sold some of these with the first one through a group by id. The second through a subquery which creates unique ids and joins onto the first one.
The issue I'm having is the third one by company. I cannot seem to create a query that works in the above combinations. Any ideas?
As suggested here is my code. It works but that's because for the company I used count which doesn't give the correct number. How else can I get the company number to come out correct?
SELECT
dep.ItemIDAPK,
dep.TotalOne,
dep.company,
company.vendname,
appd.ItemIDAPK,
appd.ItemName
FROM (
SELECT
csi.ItemIDAPK,
sum(f.TotalOne) as TotalOne,
count(f.DimCurrentcompanyID) company
FROM dbo.ReportOne F with (nolock)
INNER JOIN dbo.DSaleItem csi with (nolock)
on f.DSaleItemID = csi.DSaleItemID
INNER JOIN dbo.DimCurrentcompany cv
ON f.DimCurrentcompanyID = cv.DimCurrentcompanyID
INNER JOIN dbo.DimDate dat
on f.DimDateID = dat.DimDateID
where (
dat.date >='2013-01-29 00:00:00.000'
and dat.date <= '2013-01-30 00:00:00.000'
)
GROUP BY csi.ItemIDAPK
) as dep
INNER JOIN (
SELECT
vend.DimCurrentcompanyID,
vend.Name vendname
FROM dbo.DimCurrentcompany vend
) As company
on dep.company = company.DimCurrentcompanyID
INNER JOIN (
SELECT
c2.ItemIDAPK,
ItemName
FROM (
SELECT DISTINCT ItemIDAPK
FROM dbo.dimitem AS C
) AS c1
JOIN dbo.dimitem AS c2 ON c1.ItemIDAPK = c2.ItemIDAPK
) as appd
ON dep.ItemIDAPK = appd.ItemIDAPK
For further information my output is the following example, I know the code executes and the companyid is incorrect as I just put it with a (count) in their to make the above code execute:
Current Results:
Item Number TLS CompanyID Company Name Item Number Item Name
111111 300 303 Johnson Corp 29323 Soap
Proposed Results:
Item Number TLS CompanyID Company Name Item Number Item Name
111111 300 29 Johnson Corp 29323 Soap

SQL Query Count - Join two tables and get a count even if it is 0

Ok, working on a query in SQL 2012 right now to join two tables and get a count. The count is how many companies are associated with a primary company. This lists exists in the same table, Contact, and they are all connected as ID of the primary company is listed in the secondary company as CompanyID. I can get a count if the primary has at least 1 secondary but I can't seem to get a count if the primary has no secondary and I need to show that 0 value. Here is my SQL query:
SELECT c.ID, c.Company, c.Category, COUNT(c1.ID) AS Secondaries
FROM Contact AS c INNER JOIN Contact AS c1 ON c.ID = c1.CompanyId
WHERE (c.MemberType = 'ORG_M') AND (c1.MemberType = 'ORG_M')
GROUP BY c.ID, c.Company, c.Category
When I do this, I get this information back:
ID Company Category Count
1 Company 1 RS_1 1
2 Company 2 RS_1 1
3 Company 3 RS_1 1
4 Company 4 RS_1 1
What I am missing is the 0 value for if a company exists in the company table but has no secondary company tied to them. How do I get that?
Use an outer join instead and move the where criteria to the join:
SELECT c.ID, c.Company, c.Category, COUNT(c1.ID) AS Secondaries
FROM Contact AS c
LEFT JOIN Contact AS c1 ON c.ID = c1.CompanyId AND c1.MemberType = 'ORG_M'
WHERE c.MemberType = 'ORG_M'
GROUP BY c.ID, c.Company, c.Category

Query to select related data from two tables in which one table has no related fields in third table

I have three tables in my Oracle db:
Peoples:
IdPerson PK
Name
Surname
Earnings:
IdEarning PK
IdPerson
EarningValue
Awards:
IdAward PK
IdPerson FK
AwardDescription
So one person can have many earnings, one earning or can have no any earnings. Also one person can have many awards, one award, or no any award.
I have to select Surname and AwardDescription but only for people who have any earnings, because it is possible to have some award but, also don't have any earning!
My problem is to make a correct group by statement. I use query posted below and I am selecting surname of person with a description of award, but it is duplicating for each row in Earnings for this person.
SELECT AwardDescription, Surname
FROM Awards
INNER JOIN People ON People.IdPerson= Awards.IdPerson
INNER JOIN Earnings ON Earnings .IdPerson= People.IdPerson;
How to group it and avoid duplicating rows for each earning of person?
One person can be in many rows, but with different awards.
You could add DISTINCT to your query:
SELECT DISTINCT AwardDescription, Surname
FROM Awards
INNER JOIN People ON People.IdPerson= Awards.IdPerson
INNER JOIN Earnings ON Earnings .IdPerson= People.IdPerson;
Or another option is to use EXISTS:
SELECT AwardDescription, Surname
FROM Awards
INNER JOIN People P ON P.IdPerson= Awards.IdPerson
WHERE EXISTS (
SELECT 1
FROM Earnings E
WHERE P.IdPerson = E.IdPerson);
Do a left outer join among the tables like
SELECT p.Surname, a.AwardDescription, e.EarningValue
FROM People p
LEFT JOIN Awards a ON p.IdPerson= a.IdPerson
LEFT JOIN Earnings e ON e.IdPerson= p.IdPerson
WHERE a.AwardDescription IS NOT NULL
OR e.EarningValue IS NOT NULL;