Question

Say you have a table layout like the following:

couses:

id (INT),  courseName (VARCHAR) 

instructors:

id (INT), courseId(INT), instructor(VARCHAR) 

Create a query which will print the all the courses and if one instructor is present display their name, if two instructors are present print both of their names on the row in sorted order, if more than two instructors are present instead of the instructors names display “committee“.

For instance your output would look something like this

     courseId    instructor1        instructor2      0           Edward Yourdon       1           Edward Dijkstra    Nicholas Wirth      2           Comittee     

Note: Taken from a questionnaire on TheDailyWtf. Not a homework question.

Answer 1

In SQL Anywhere, here’s how you could do it:

select courseid as cid, if ( select count(*) from instructor where courseid = cid ) > 2     then 'Committee'  else     list(name order by name)  endif as profs from instructor group by courseid order by cid  

Note that this selects ‘profs’ as the list of professors (as stated in the question) as a single column.

I’m not familiar enough with MySQL to know if there is an equivalent to the list() function.