Abstract
Structured Query Language (SQL) is the most widely used declarative
language for accessing relational databases, and an essential topic in introductory
database courses in higher learning institutions. Despite the intuitiveness
of SQL, formulating and comprehending written queries can be confusing,
especially for undergraduate students. One major reason for this is that the
simple syntax of SQL is often misleading and hard to comprehend. A number of
tools have been developed to aid the comprehension of queries and improve the
mental models of students concerning the underlying logic of SQL. Some of these
tools employed visualisation and animation in their approach to aid the comprehension
of SQL. This paper presents an interactive comprehension aid based
on visualisation, specifically designed to support the SQL SELECT statement, an
area identified in the literature as problematic for students. The visualisation
tool uses visual specifications depicting SQL operations to build queries. This
is expected to reduce the cognitive load of a student who is learning SQL. We
have shown with an online survey that adopting visual specifications in teaching
systems assist students in attaining a richer learning experience in introductory
database courses.