Question

I’m new to SQL and I am having trouble even starting this query.

If a student has a record in ‘2012’, list that record and all of their previous records.

A simplified data set:

ASSIGNMENTS

STUDENT_ID    BOOK_TITLE   TERM
001           MOBY DICK    2009     
002           ULYSSES      2009
003           HAMLET       2009
004           1984         2009
005           HAMLET       2009
004           WAR & PEACE  2010
003           THE TRIAL    2010
004           MOBY DICK    2011
001           -NULL----    2012
004           -NULL----    2012

Results should be the record of those registered in a given term followed by that student’s previous records. The goal is for the user to look at currently registered students (NULL value in book title) and make sure they don’t assign a book the student has already read.

STUDENT_ID   BOOK_TITLE   TERM

001          -NULL----    2012

001          MOBY DICK    2009

004          -NULL----    2012

004          MOBY DICK    2011

004          WAR & PEACE  2010

004          1984         2009

Any pointers/starting directions would be greatly appreciated! I have tried messing around with 'with', multiple inner joins, but I am not getting anywhere. I keep thinking about if..then syntax that doesn't really work in SQL?

Answer 1

SELECT STUDENT_ID, BOOK_TITLE, TERM
  FROM ASSIGNMENTS
  WHERE STUDENT_ID IN
   (SELECT DISTINCT STUDENT_ID FROM ASSIGNMENTS WHERE TERM = 2012)
  ORDER BY STUDENT_ID, TERM DESC

To come up with this answer first I created a query that matched your expected result format. Then I added the where criteria for “only students currently registered”.

If you want to parameterize it put @Term instead of 2012. You could also run it off null book titles using WHERE BOOK_TITLE IS NULL