The automatic checking of online assessments and tutorials offers a significant advantage to students. Such students can work out-of-hours, from home or work, managing their own time allocation. This allows formal practical sessions to concentrate on learning, and not on assessments. However, there is a danger that students will abuse such systems, invalidating the assessment process. This paper investigates the plagiarism detected in a learning environment for SQL, and the effectiveness of the different techniques that it has used to eliminate plagiarism.