Localizing Faults in SQL Predicates

Fault localization techniques have been applied to database and data-centric applications that use SQL or SQL-based languages. However, existing techniques can only identify the SQL statements that have faults, but not determine the precise location of the faults within SQL statements. Since SQL statements can be rather complex, programmers are still left with a difficult repair chore. We propose a novel fault localization method to localize multiple types of faults in SQL predicates, that is based on row-based dynamic slicing and delta debugging. Our method was implemented in a tool called ALTAR, and experiments were performed on two publicly available databases. Our method can be compared with existing fault localization techniques when these are applied to "drill-down" in SQL statements. The results showed that ALTAR can discover more types of faults. Moreover, for the type of faults discovered by current methods, ALTAR is more precise.