Extensions relatoinal model Flashcards
What is Relational Algebra?
A procedural query language based on set theory, used to define operations on relations like SELECT, PROJECT, JOIN. It specifies how data is retrieved through algebraic operations on relations.
What is Relational Calculus?
A non-procedural, logic-based query language that describes what data is required using predicate logic. Supports TRC and DRC.
What is DML?
Data Manipulation Language, SQL subset for managing table data during runtime. (e.g., SELECT, INSERT, UPDATE, DELETE).
What is DCL (Data Control Language)?
SQL commands (GRANT, REVOKE) for managing user permissions and security on database objects.
What are Procedural Extensions in SQL?
Enhancements like loops, conditionals, and exception handling that allow writing procedures, functions, and triggers in SQL.
What are Active Behaviours in databases?
Event-driven actions (e.g., triggers) that run automatically when specified events like INSERT, UPDATE, or DELETE occur.
What is External Design in databases?
Defines user-specific views and how users interact with data without exposing the entire logical schema.
What is Physical Design in databases?
The actual storage layout including indexing and partitioning, aimed at optimizing performance and access speed.
What is a View in SQL?
A virtual table generated by a query. Used for simplified data access, enhanced security, and abstraction.
What is a Base Relation?
A real table physically stored in the database, forming the primary data source for operations and queries.
What does Cardinality refer to in databases?
The number of rows (tuples) in a relation, used to measure and optimize performance.
What is Relation Fusion?
Combining data from multiple relations into a unified set using operations like JOIN, UNION, or schema merging.
What is a Materialized View?
A physical copy of a query result stored in the database to improve performance. Can be refreshed automatically or manually.
What are Snapshots in databases?
Static copies of data at a specific point in time, used for backup, reporting, and historical analysis.
What are Temporal Relations?
Relations that include time-based data (valid time, transaction time) to support historical and future queries.
What is a Declared Cursor?
A programmer-defined cursor in SQL that allows row-by-row retrieval with explicit control using OPEN, FETCH, CLOSE.
What is a Created Cursor?
A cursor declared and instantiated inside a SQL block or procedure for controlled row-wise data processing.
What is a Parameterized Cursor?
A cursor that accepts parameters to make its query logic dynamic, based on passed values during execution.
What is an Implicit Cursor?
A system-managed cursor used internally for single-row operations like SELECT INTO, INSERT, UPDATE, or DELETE.
What is a Package in PL/SQL?
A modular collection of related procedures, functions, and variables grouped together for reuse and organization.
What is a Trigger in SQL?
A procedural block that executes automatically in response to events like INSERT, UPDATE, DELETE on a table/view.
What is a Mutating Table?
A table being modified and queried simultaneously within a trigger, causing runtime errors and inconsistencies.
What is DDL (Data Definition Language)?
SQL subset (CREATE, ALTER, DROP) used to define and manage database schema structures. Changes are auto-committed.
What is Dynamic Programming?
An optimization technique that solves complex problems by breaking them into overlapping subproblems and storing solutions.
