Database Concepts Review

These flashcards cover important vocabulary and concepts related to databases, particularly focusing on relational databases, indexing, concurrency control, and recovery methods.

Relation R(A, B, C)

A set of tuples that holds data where each tuple has values for attributes A, B, and C.

Division Operator ( ÷ )

An operator that takes two relations and returns a relation consisting of tuples from the first relation that are associated with tuples in the second relation.

Query to retrieve female employee names

A query that filters records based on the sex attribute to return only the first name and last name of employees where sex is 'F'.

Relational Algebra

A formal query language used to manipulate and retrieve data from relational databases using operations like selection (σ), projection (π), and join (⨝).

Blocking Factor (bfr)

The number of records that can be stored in one disk block, calculated by the formula bfr = floor(B/R) where B is the block size and R is the record size.

Multilevel Index

An index structure that allows for faster searching by indexing the index entries themselves, creating levels of indices for more efficient data retrieval.

Clustering Index

An index that maintains the order of the data file based on non-key fields, allowing for efficient access to groups of related records.

Primary Index

An index that is directly associated with the data file organized based on the key attribute that uniquely identifies records.

Hashing

A technique that uses a hash function to map data to a fixed size, facilitating rapid retrieval.

B+-tree

A self-balancing tree data structure that maintains sorted data and allows for efficient insertion, deletion, and search operations, specifically optimized for disk storage.

Conflict Serializable Schedule

A schedule that ensures the same results as some serial schedule, maintaining the order of conflicting operations in transactions.

Two-Phase Locking (2PL) Protocol

A concurrency control method that ensures transactions are executed in a safe manner by acquiring all required locks before starting execution and releasing them after.

Cascading Rollback

A situation in transaction processing where the failure of one transaction forces operations in other transactions to be undone.

Search Key

An attribute or combination of attributes used to retrieve or reference records in a database efficiently.

True/False Indexing

A process through which attributes of a database are indexed based on conditions to improve query performance.

Recovery in Databases

Methods and procedures used to restore a database to a previous consistent state after a failure.

Dirty Read

A situation where a transaction reads data that has been written by another ongoing transaction, which may be rolled back later.

Shadow Paging

A recovery technique where updates to the database are made only to a temporary location, which becomes the current version if the transaction commits.

Active Database

A database that automatically reacts to certain conditions by triggering rules or actions.