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;
Related
I am learning postgresql and Inner join I have following table.
Employee
Id Name DepartmentId
1 John S. 1
2 Smith P. 1
3 Anil K. 2
Department
Department
Id Name
1 HR
2 Admin
I want to query to return the Department Name and numbers of employee in each department.
SELECT Department.name , COUNT(Employee.id) FROM Department INNER JOIN Employee ON Department.Id = Employee.DepartmentId Group BY Employee.department_id;
I dont know what I did wrong as I am new to database Query.
When involving all rows or major parts of the "many" table, it's typically faster to aggregate first and join later. Certainly the case here, since we are after counts for "each department", and there is no WHERE clause at all.
SELECT d.name, COALESCE(e.ct, 0) AS nr_employees
FROM department d
LEFT JOIN (
SELECT department_id AS id, count(*) AS ct
FROM employee
GROUP BY department_id
) e USING (id);
Also made it a LEFT [OUTER] JOIN, to keep departments without any employees in the result. And COALESCE to report 0 employees instead of NULL in that case.
Related, with more explanation:
Query with LEFT JOIN not returning rows for count of 0
Your original query would work too, after fixing the GROUP BY clause:
SELECT department.name, COUNT(employee.id)
FROM department
INNER JOIN employee ON department.id = employee.department_id
Group BY department.id; --!
That's assuming department.id is the PRIMARY KEY of the table, in which case it covers all columns of that table, including department.name. And you may want LEFT JOIN like above.
Aside: Consider legal, lower-case names exclusively in Postgres. See:
Are PostgreSQL column names case-sensitive?
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
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.
I have three tables in my Oracle db:
Peoples:
IdPerson PK
Name
Surname
Earnings:
IdEarning
IdPerson
EarningValue
Awards:
IdAward PK
IdPerson FK
AwardDescription
A person can have many earnings.
An earning can have many or no any earnings.
A person can have many awards, one award, or no any award.
I want to make a query that will return 3 columns:
Surname
SUM of all EarningValue of person with this surname
COUNT of all Awards for this person
An important thing is that i also need to display: 0 value if person don't have any award or earning. There is a possibility that person have an award but don't have any earning.
Is it possible to make such query?
SELECT p.IdPerson,
p.Surname,
NVL(SUM(e.EarningValue), 0) as SumEarnings,
COUNT(a.IdAward) as CntAwards
FROM Peoples p
LEFT JOIN Earnings e ON p.IdPerson = e.IdPerson
LEFT JOIN Awards a ON p.IdPerson = a.IdPerson
GROUP BY p.IdPerson,
p.Surname;
What returns this:
SELECT p.Surname,
(SELECT NVL(SUM(e.EarningValue), 0)
FROM Earnings e WHERE e.IdPerson = p.IdPerson) as SumEarnings,
(SELECT COUNT(aIdAward)
FROM Awards a WHERE a.IdPerson = p.IdPerson) as CntAwards
FROM Peoples p
yes of-course it is possible.
you just need to join the tables using multiple join queries and then apply sum() function to get sum of earnings and Count() to count the no. of awards.
Try the below query:
SELECT P.Surname,
Sum(E.EarningValue)AS Total_Earnings,
Count(A.IdAward) AS total_awards
FROM Peoples P
LEFT JOIN Earnings E
ON P.IdPerson = E.IdPerson
LEFT JOIN Awards A
ON A.IdPerson = P.IdPerson
GROUP BY P.IdPerson;
Yes it is possible, you just have to join the tables
SELECT Peoples.Surname, SUM(Earnings.EarningValue) as Earnings, COUNT(Awards. IdPerson) as Awards
FROM Peoples
INNER JOIN Earnings
ON Peoples.IdPerson = Earnings.IdPerson
INNER JOIN Awards
ON Peoples.IdPerson = Awards.IdPerson
GROUP BY Peoples.IdPerson;
Ok I have two tables.
One table is called Persons and just has columns Pname and Age. (A person's name and their age).
Another table is called Giving and has donor, receiver, and giftname. (donor and receiver have foreign key constraints referencing persons.pname).
I need to find the names of all people who donated a gift to someone with a different age.
SELECT
Giving.donor
FROM Giving
INNER JOIN Persons AS donor ON Giving.donor=donor.Pname
INNER JOIN Persons AS receiver ON Giving.receiver=receiver.Pname
WHERE donor.Age<>receiver.Age
If you mean the donor age has to be different then the receiver age, then try this:
SELECT pd.pname
FROM Persons pd
INNER JOIN giving g
ON pd.pname = g.donor
INNER JOIN persons pr
ON pr.pname = g.receiver AND pr.age != pd.age