DBSnap: Learning database queries by snapping blocks

A significant amount of recent research in Computer Science Education has focused on studying block-based programming. In this approach, computer programs are created by connecting blocks and the blocks' shapes determine the permitted connections. The focus is on the program's logic instead of its syntax. This paper introduces DBSnap, a web-based application to build database queries, particularly relational algebra queries, by snapping blocks. DBSnap fully supports the construction of intuitive database query trees, which is one of the most effective approaches to teach database queries. DBSnap is also highly dynamic and shows the query results as the query is being built. The user can also inspect, at any time, the intermediate results of any query node. This paper presents DBSnap's design and implementation details, an evaluation of its effectiveness as a learning environment, and a thorough comparison with alternative ways to teach query languages. DBSnap is publicly available and aims to have the same transformational effect on database learning as previous block-based systems had on traditional programming learning.