SQL Fundamentals

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Lab4 objectives100 XP

16.Translate Division

PostgreSQL-specific syntax on this page. Each spot is marked with the MySQL form.

The pattern for r ÷ s in SQL: keep a tuple t of r when nothing in s is missing for t.

severy tuple of

EXCEPT

rwhat t has in

=

NOT EXISTSmust be empty

r ÷ s in SQL

π id, semester, year (teaches) ÷ π semester, year (teaches): the instructors who teach in every term that appears in teaches.
π id, course_id (takes) ÷ ρ need(course_id) (π prereq_id (σ course_id = 'CS-340' (prereq))): the students who took every prerequisite of CS-340.
What is the name of that student?
No course has dept_name 'Art'. How many tuples does π id, course_id (takes) ÷ π course_id (σ dept_name = 'Art' (course)) return?

Something unclear, wrong or missing?

Databaselab-db · PostgreSQL in your browser 0:00

SELECT semester, year FROM teaches;

Ctrl↵runs the query · select text to run part of it

Objective 1 of 40/4 done

Instructors who teach in every term
π id, semester, year (teaches) ÷ π semester, year (teaches). One column: id.