Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 8 years ago.
Improve this question
I am working for the IT Department of a college as a student worker and have very limited knowledge in using SQL (I am not majoring in Computer Science/Engineering). I'll try my best to describe what I want to accomplish here.
I want to create a table that includes info about new students, basically : id, first name, last name, need exams (Y/N), Course101 section, instructor.
My problem is, exchange and transfer students and also some first year students would not have to/did not sign up for Course101, so using WHERE studnt_course = 'Course101%' will leave out those students. I would like to pick up those students in my view and display their Course101 section, Instructor values as Null.
I am thinking about making two views, one for all new students, and one for students with Course101 only, and do some kind of merging/union but not sure how to actually do that.
Any help will be greatly appreciated!
It's still a bit vague what the current tables actually look like which makes it hard to give a good suggestion.
Based on what you've given us I'd suggest looking into a LEFT INNNER JOIN which would put NULL where the two tables don't overlap.
If you are interested in learning database design (rather than just solving this particular problem) I'd suggest looking into proper database design.
Create two queries. One for the 101 students and one for the overseas/transfers (you will need to work out what the WHERE clause if for that)
Get each one working to your satisfaction.
If every thing is the same apart from the WHERE clause then:
Then grab the conditions for each, wrap them in brackets and put an OR in between, put that into one query
So something like:
SELECT Name, Id,ShoeSize
FROM Students
WHERE (studnt_course = 'Course101%') OR (transferred = 1 OR is_exchange = 1)
i.e., So all students WHERE <this> OR <that> is true
Other wise (e.g., using diffrent tables):
Make sure that you are selecting the same column names in you SELECT statement
If one column has the same info but is call some thing different you can go:
<columnName> AS <NameYouWantToCallIt>
Make sure the column names are in the same order.
Then put the word UNION in-between the two queries.
This will combine the results from both queries (and remove duplicates).
SELECT Name, Id, ShoeSize
FROM Students
WHERE studnt_course = 'Course101%'
UNION
SELECT Name, Id, FootSize AS ShoeSize
FROM exchangeStudents
WHERE transferred = 1 OR is_exchange = 1
Related
My current test revolves around a hypothetical database consisting of a PERSON table populated with their details.
I can undertake a simple LIKE query were I return the details of say a person or persons named Tom.
My question is how can I build a query were there may be multiple names and return their details?
I my exercise there is a checkbox list of names and I need to return the details for all those I select?
Thank you in advance for your assistance.
I'm using Tableau to show some schools data.
My data structure gives a table that has all de school classes in the country. The thing is I need to count, for example, how many schools has Primary and Preschool (both).
A simplified version of my table should look like this:
In that table, if I want to know the number needed in the example, the result should be 1, because in only one school exists both Primary and Preschool.
I want to have a multiple filter in Tableau that gives me that information.
I was thinking in the SQL query that should be made and it needs a GROUP BY statement. An example of the consult is here in a fiddle: Database example query
In the SQL query I group by id all the schools that meet either one of the conditions inside de IN(...) and then count how many of them meet both (c=2).
Is there a way to do something like this in Tableau? Either using groups or sets, using advanced filters or programming a RAW SQL calculated fiel?
Thanks!
Dubafek
PS: I add a link to my question in Tableu's forum because you can download my testing workbook there: Tableu's forum question
I've solved the issue using LODs (specifically INCLUDE and EXCLUDE statements).
I created two calculated fields having the aggregation I needed:
Then I made a calculated field that leaves only the School IDs that matches the number of types they have (according with the filtering) with the number of types selected in the multiple filter (both of the fields shown above):
Finally, I used COUNTD([Condition]) to display the amounts of schools matching with at least the School types selected.
Hope this helps someone with similar issue.
PS: If someone wants the Workbook with the solution I've uploaded it in an answer in the Tableau Forum
Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 5 years ago.
Improve this question
We discovered wrong data in one of our table and we would like to identify them.
We have 4 tables:
Student
School
School_Student
Location
The relation between them as follow
Each location has many schools
Each student can be in different schools in the same location
Due that some students have the same name although they are different persons with different ID, we found that some students are assigned to different schools in different locations
You can see in the screenshot that "Adam Mike" is assigned to 3 different schools, the second and the third line are ok because the location of the school is the same however the first line is not ok because the school is in a different location.
so i would like to have a query that returns all students that are assigned to different locations so that i can manually correct them.
Thank you
EDIT
In my last question Find duplication in multi tables
the student cannot be in different school.
To make it more clear.
In this screenshot you see that all records with "?" are not correct because the location is different.
So mike cannot be in a school in USA and in GB
in the otherhand JIM is in different schools but in the same location so this is ok
Now i would like to find all records where students has records in different locations.
Try something like. It returns the students that have more than 1 unique location.
SELECT ss.student_id
FROM school s
JOIN school_student ss
ON s.id = ss.school_id
GROUP BY ss.student_id
HAVING COUNT(DISTINCT s.location_id) > 1
Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 9 years ago.
Improve this question
When I use below query to add new record to the table (at unknown), the new records added to first of table .
I want to add new records to the last of table .
this my code :
begin
insert into TBLCrowler (Url,Title,ParentId,HasData) values (#Url,#Title,#ParentId,#HasData)
end
select top 1 CatId, Title, ParentId, Url, CrawlerCheck from TBLCrowler where CatId=(Select min(CatId) from TBLCrowler where CrawlerCheck=1)
update TBLCrowler set CrawlerCheck=2 , HasData=2
where CatId=(Select min(CatId) from TBLCrowler where CrawlerCheck=1)
Okay, once more into the breach.
You are using a relational database. It's not a worksheet, it's not a rectangular array of cells in a word document. It's power is reliant on being able to store and retrieve records in the most efficient way possible.
Ordering is either implied through an index, which the DBMS is free to ignore, and which could change anyway, or explicitly required through an order by statement
If you want things ordered by the time they were added to the table, you add a created_at column and populate it at the time you perform the insert.
Then when you select from it you add Order By Created_At to your select statement.
If you want that ordering to be "fast" you add an index on the Created_At column, which then DBMS will make a brave attempt at using the index in order to avoid the cost of a full pass sort.
Step back and think for a minute about how you would write a DBMS. What would the cost of your implicit orderedness be. Any change to any but the "last" record in the "last" table would mean rewriting to disk every record in every table "after" it. Insert is worse, Delete is as bad and that's without considering that different records take up different amounts of space.
So throw first and last in the bin, if you can find them...
I am designing an online math quiz for a college project and having some trouble with designing my database.
The basic idea of the website is as follows:
A teacher, once registered may log in and add questions to their account. They can choose between making the questions multiple choice OR true or false. They can also choose between making their questions public or private. (If they choose to make the questions public, other teachers may view the questions.)
At any time the teacher may create a quiz for their students using the questions in their private bank and / or questions from the public bank. Each question may be used in multiple quizzes.
The idea is that the students will later log in and do the quiz; their answers are stored and the teacher can generate reports and check how the students did individually / highest and lowest scoring questions etc.
I am having some trouble deciding how to store the quizzes and questions which I hope somebody may be able to help me with.
So far I have the following:
‘Question’ table with attributes: QuestionID, SubjectArea, Concept, QuestionText, TeacherID, QuestionType, PublicYorN
‘MCQuestions’ table with attributes: QuestionID, AnsA, AnsB, AnsC, AnsD, AnsE, CorrectAns
‘TorFQuestions’ table with attributes: QuestionID, CorrectAns
‘Quiz’ table with attributes: QuizID, CreationDate, TeacherID
I think I then need another table as follows:
‘QuizQuestions’ and the only attributes will be QuizID, QuestionID which together make a concatenated primary key.
I feel like I should have a separate table to store answers to questions and I'm not sure if I need to separate true or false questions and multiple choice questions as I have done above.
(Obviously there are other tables containing user data etc. but this is the part I’m concerned with.)
Any advice / input is greatly appreciated!
A simple yet flexible design would be something like this:
Questions table (id, text, correct answer id, all the other question related data)
Answers table (id, question id text, all the other answer related data)
Quiz table (id, text, all the other quiz related data)
Quiz questions table (quiz id, question id, question display order, other related data such as question weight might also be added)
Quiz results table (quiz id, question id, answer id, user id, all the other related data such as date of answer and such).
I think my only input to this open ended question is:
Combine MCQuestions and TorF Questions to have a different format. Answers table has 4 cols. QID, AnswerID,answer,Correct Y/N.
Then a true or false question has 2 rows - eg. QID=888, AID=1,Ans=TRUE,true. Next row is QID=888, AID=2,Ans=FALSE,false.
Multiple choice has several - so which is the bright yellowy thing? QID=889, AID=3,Ans=Moon,false. QID=889, AID=4,Ans=Sun,true. QID=889, AID=5,Ans=Mars,false.
Then you grab a list of answers and can populate a set of radio buttons with the QID and AID values. Then you are matching integers in your code rather than long text strings which will need to be passed around for matching. Might make it a bit easier in case of special chars in the answers or whatever and you're matching the quiz results to a unique key.
Apart from that minor change it's difficult to help without knowing any other constraints...
Nick