Databases for GATE

Databases is the most procedural subject in the paper: almost every question has a fixed method, and the marks go to whoever applies it without slipping. Candidate key finding and highest-normal-form identification appear almost every year, and both depend on computing attribute closures correctly and finding every candidate key rather than just one. SQL questions concentrate on where theory and practice diverge, namely set versus multiset semantics and three-valued logic with nulls, which is where the NOT IN trap lives. B-plus tree order computation is a near-certain numerical and hinges on computing the internal and leaf orders separately. Serializability is decided by a precedence graph cycle check, which takes a minute and cannot go wrong if the conflicting pairs are listed item by item.