Imagine I have a query called QueryA that returns stuff like this:
Employee Description Rank
John Happy 1
John Depressed 3
James Happy 1
James Confused 2
Mark Depressed 3
I am trying to make a query that grabs the Employee and the Description, but only one description -- the one with the best "rank." (the lower the rank the better). I sort QueryA by Employee then by Rank (descending).
So I'd want my new query QueryB to show that John as Happy, James as Happy, and Mark as Depressed.
However I try selecting Employee and then First of Description and it doesn't always work.
I'm not able to check this for Access, but it should work fine. Check my SQL Fiddle
select
r.employee, d.description
from
table1 as d
inner join (select min(rank) as rank, employee
from
table1
group by employee) r on d.rank = r.rank
and d.employee = r.employee
Related
I'm sorry for asking these questions but I am really new and studying Oracle SQL for my university and I am having a hard time with a few things. Anyways, for this one, I am supposed to retrieve data from 2 different tables. One is from 'STAFF' and one is from 'BRANCH' I want the output to display the staff name (SNAME), the start date (STARTDATE) and the area (AREA). SNAME and STARTDATE are from the table 'STAFF', and the AREA is from the table 'Branch', how do I access that? Also, I ONLY want to display the names and start dates of those who are in the STOKE areea.
This is my code
SELECT SNAME, STARTDATE, BRANCH.AREA
FROM STAFF CROSS JOIN BRANCH
WHERE STAFF.BRANCHID = 20;
Note: The STAFF.BRANCHID = 20 is because the area 'STOKE' has a BRANCHID of 20.
This is what I get:
SNAME STARTDATE AREA
---------- --------- -------------
SMITH 15-NOV-00 ECCLESHALL
JONES 02-MAR-01 ECCLESHALL
SONG 03-JAN-02 ECCLESHALL
SMITH 15-NOV-00 STOKE
SONG 03-JAN-02 STOKE
SMITH 15-NOV-00 STAFFORD
As you can see, the WHERE clause is not working because it outputs every area instead of stoke only.
I know I am supposed to use the JOIN function but I don't get which one and why, any useful links would be appreciated :)
Thank you
You need to use the INNER JOIN and proper join condition as follows:
SELECT S.SNAME, S.STARTDATE, B.AREA
FROM STAFF S INNER JOIN BRANCH B
ON S.BRANCHID = B.BRANCHID
WHERE S.AREA = 'STOKE';
This is my first month of being a Data Analyst, and I can't seem to find an answer that is specific enough to my problem here to help. I am having trouble getting this manager flag field to work and I think I'm getting confused by the joins.
The goal is to match the EMPLIDs of JOB_VW A to see if they exist in the Supervisor_ID column of Supervisor_VW K. Supervisor_VW K has ALL employees in the company (including supervisors) in the K.EMPLID column. Someone can be in both the supervisor ID column and EMPL column at the same time, but in different rows. The SUP ID is the EMPL ID of someone in a manager position.
For example:
Supervisor_VW K
EMPL ID EMPL NAME SUP ID SUP NAME
1 Smith, John 2 William, Mark
5 Jarvis, John 2 William, Mark
2 William, Mark 4 Rover, Spot
The results I am getting are as such
QUERY RESULTS
EMPLID EMPL NAME MANAGER FLAG
2 William, Mark Y
2 William, Mark Y
4 Rover, Spot Y
1 Smith, John N
5 Jarvis, John N
My current code is as follows:
SELECT CASE WHEN K.Supervisor_Id IS NULL THEN
'N'
ELSE
'Y'
END AS "ManagerFlag".....
FROM (SELECT K.*
FROM SUPERVISOR_VW K, JOB_VW A
WHERE K.SUPERVISOR_ID (+) = A.EMPLID
AND EXISTS (SELECT K1.EMPLID, K1.SUPERVISOR_ID
FROM SUPERVISOR_VW K1
WHERE K1.EMPLID IN K1.Supervisor_Id)
) K
So it seems that I am getting duplicate supervisor rows for every single employee that they supervise. If they supervise only one person, I get a singular row. If they supervise 20, I get 20 duplicate rows of that supervisor. HOWEVER, their employee that they supervise shows up in the table without issue and is properly labeled as N, no duplicates.
If anyone could help, please do! I appreciate you reading through my work, let me know if more info is required.
The usual way to achieve the desired result is like this:
select emplid, emplname,
case when emplid in (select supid from supervisor_vw) then 'Y'
else 'N' end as managerflag
from supervisor_vw;
I want to find how many modules a lecturer taught in a specific year and want to select name of the lecturer and the number of modules for that lecturer.
Problem is that because I am selecting Name, and I have to group it by name to make it work. But what if there are two lecturers with same name? Then sql will make them one and that would be wrong output.
So what I really want to do is select name but group by id, which sql is not allowing me to do. Is there a way around it?
Below are the tables:
Lecturer(lecturerID, lecturerName)
Teaches(lecturerID, moduleID, year)
This is my query so far:
SELECT l.lecturerName, COUNT(moduleID) AS NumOfModules
FROM Lecturer l , Teaches t
WHERE l.lecturerID = t.lecturerID
AND year = 2011
GROUP BY l.lecturerName --I want lectureID here, but it doesn't run if I do that
SELECT a.lecturerName, b.NumOfModules
FROM Lecturer a,(
SELECT l.lecturerID, COUNT(moduleID) AS NumOfModules
FROM Lecturer l , Teaches t
WHERE l.lecturerID = t.lecturerID
AND year = 2011
GROUP BY l.lecturerID) b
WHERE a.lecturerID = b.lecturerID
You should probably just group by lecturerID and include it in the select column list. Otherwise, you're going to end up with two rows containing the same name with no way to distinguish between them.
You raise the problem of "wrong output" when grouping just by name but "undecipherable output" is just as big a problem. In other words, your desired output (grouping by ID but giving name):
lecturerName Module
------------ ------
Bob Smith 1
Bob Smith 2
is no better than your erroneous output (grouping by, and giving, name):
lecturerName Module
------------ ------
Bob Smith 3
since, while you now know that one of the lecturers taught two modules and the other taught one, you have no idea which is which.
The better output (grouping by ID and displaying both ID and name) would be:
lecturerId lecturerName Module
---------- ------------ ------
314159 Bob Smith 1
271828 Bob Smith 2
And, yes, I'm aware this doesn't answer your specific request but sometimes the right answer to "How do I do XYZZY?" is "Don't do XYZZY, it's a bad idea for these reasons ...".
Things like writing operating systems in COBOL, accounting packages in assembler, or anything in Pascal come to mind instantly :-)
You could subquery your count statement.
SELECT lecturername,
(SELECT Count(*)
FROM teaches t
WHERE t.lecturerid = l.lecturerid
AND t.year = 2011) AS NumOfModules
FROM lecturer l
Note there are other ways of doing this. If you also wanted to elimiate the rows with no modules you can then try.
SELECT *
FROM (SELECT lecturername,
(SELECT Count(*)
FROM teaches t
WHERE t.lecturerid = l.lecturerid
AND t.year = 2011) AS NumOfModules
FROM lecturer l) AS temp
WHERE temp.numofmodules > 0
I am looking at making a simple leader board for a time trial. A member may perform many time trials, but I only want for their fastest result to be displayed. My table columns are as follows:
Members { ID (PK), Forename, Surname }
TimeTrials { ID (PK), MemberID, Date, Time, Distance }
An example dataset would be:
Forename | Surname | Date | Time | Distance
Bill Smith 01-01-11 1.14 100
Dave Jones 04-09-11 2.33 100
Bill Smith 02-03-11 1.1 100
My resulting answer from the example above would be:
Forename | Surname | Date | Time | Distance
Bill Smith 02-03-11 1.1 100
Dave Jones 04-09-11 2.33 100
I have this so far, but access complains that I am not using Date as part of an aggregate function:
SELECT Members.Forename, Members.Surname, Min(TimeTrials.Time) AS MinOfTime, TimeTrials.Date
FROM Members
INNER JOIN TimeTrials ON Members.ID = TimeTrials.Member
GROUP BY Members.Forename, Members.Surname, TimeTrials.Distance
HAVING TimeTrials.Distance = 100
ORDER BY MIN(TimeTrials.Time);
IF I remove the Date from the SELECT the query works (without the date). I have tried using FIRST upon the TimeTrials.Date, but that will return the first date which is normally incorrect.
Obviously putting the Date as part of the GROUP BY would not return the result set that I am after.
Make this task easier on yourself by starting with a smaller piece of the problem. First get the minimum Time from TimeTrials for each combination of MemberID and Distance.
SELECT
tt.MemberID,
tt.Distance,
Min(tt.Time) AS MinOfTime
FROM TimeTrials AS tt
GROUP BY
tt.MemberID,
tt.Distance;
Assuming that SQL is correct, use it in a subquery which you join back to TimeTrials again.
SELECT tt2.*
FROM
TimeTrials AS tt2
INNER JOIN
(
SELECT
tt.MemberID,
tt.Distance,
Min(tt.Time) AS MinOfTime
FROM TimeTrials AS tt
GROUP BY
tt.MemberID,
tt.Distance
) AS sub
ON
tt2.MemberID = sub.MemberID
AND tt2.Distance = sub.Distance
AND tt2.Time = sub.MinOfTime
WHERE tt2.Distance = 100
ORDER BY tt2.Time;
Finally, you can join that query to Members to get Forename and Surname. Your question shows you already know how to do that, so I'll leave it for you. :-)
Simple structure table of employees
Employee Manager
Joe Smith Jon Smith
Jon Smith Pete Stevens
Pete Stevens NULL
Jared Scho Pete Stevens
....
Im just trying to return some results but I want an indicator on whether the person is a manager or not so the result should be:
Employee Manager IsAManager
Joe Smith Jon Smith 0
Jon Smith Pete Stevens 1
Pete Stevens NULL 1
Jared Scho Pete Stevens 0
The result set is showing that Joe Smith and Jared Scho are not managers...
So If I had a simple SQL Query
SELECT
Employee,
Manager,
As IsAManager --tried to do a case statement here....
FROM
Employee
I tried to do a case statement something to this effect:
SELECT CASE ISNULL(COUNT(*), 0) > 0 THEN 1 ELSE 0 END FROM Employee WHERE Manager = Employee
Not sure how to word it :)
Hopefully this is just a demo example not your real table structure.
SELECT Employee,
Manager,
CASE
WHEN EXISTS(SELECT *
FROM Employee e2
WHERE e2.Manager = e1.Employee) THEN 1
ELSE 0
END As IsAManager
FROM Employee e1
For details of how SQL Server processes EXISTS Subqueries in CASE Expressions see this article.
To determine whether an employee is a manager, you need to match the Employee's ID (in this case, the name) against the list of Manager IDs (in this case the Manager column). If you find a match, the employee is a manager. If you don't find a match, the employee is not a manager.
You can do this with a LEFT OUTER JOIN as shown here:
SELECT DISTINCT
E.Employee,
E.Manager,
CASE WHEN M.Employee IS NULL THEN 0 ELSE 1 END As IsAManager
FROM
Employee E LEFT OUTER JOIN Employee M
ON E.Employee = M.Manager
Please note the following:
You did not specify the SQL product you're using, so I tried to make the solution general. I'm guessing from your attempt to use ISNULL that it's SQL Server, but this solution should work in any product that supports CASE.
Your method of storing manager status has one problem, which is that you cannot represent a manager with no employees (you derive the manager status from the existence of the employee-manager relationship). If you want to be able to store manager status separately from the employee-manager relationship then CREATE TABLE Managers (Employee. . . PRIMARY KEY). This will make the code necessary to get back manager status a little easier to write as well.