Database glossary: Master level
24 Database terms at the Master level, each with a short definition and a link to its full page.
Updated
- Antijoin
- A relational operation returning rows from one side that have no match on the other side.
- Cartesian Product
- The relation containing every possible concatenation of a tuple from each input relation.
- Conflict Serializability
- Serializability established by reordering nonconflicting operations into a serial schedule.
- Domain Relational Calculus
- A declarative formal query language using variables that range over domain values.
- Equijoin
- A theta join whose condition uses equality.
- Natural Join
- A join matching equally named columns automatically and returning one copy of each matched column.
- Precedence Graph
- A directed graph of transaction conflicts used to test conflict serializability.
- Projection (Relational Algebra)
- The relational operation that keeps selected attributes and removes duplicate tuples.
- Relational Algebra
- A formal collection of operations that take relations as input and produce relations.
- Relational Closure
- The property that relational operations return relations.
- Relational Completeness
- The ability of a query language to express every operation of relational algebra.
- Relational Difference
- The tuples present in the first compatible relation but absent from the second.
- Relational Model
- A data model representing information through relations, domains, keys, and integrity rules.
- Selection (Relational Algebra)
- The relational operation that keeps tuples satisfying a predicate.
- Semijoin
- A relational operation returning rows from one side that have a match on the other side.
- Serial Schedule
- A transaction schedule that completes each transaction before starting the next.
- Serializable Schedule
- A concurrent schedule with the same effect as some serial schedule.
- Theta Join
- A join defined by an arbitrary comparison predicate between its inputs.
- Three-Valued Logic
- SQL logic in which a condition can be true, false, or unknown.
- Tuple Relational Calculus
- A declarative formal query language describing desired tuples with logical predicates.
- Two-Phase Locking
- A protocol where a transaction acquires locks before entering a phase that only releases them.
- Unknown Truth Value
- The third SQL truth value produced when NULL prevents a condition from being known true or false.
- View Serializability
- Serializability based on transactions reading the same values and producing the same final writes.
- Write-Ahead Logging
- A recovery rule requiring log records to reach durable storage before related data changes.