# Database flash cards: Freelancer level

43 Database terms at the Freelancer level, as flash cards.

Updated: September 27, 2026

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## Terms in this deck

- [Attribute](https://www.ask-codey.com/glossary/attribute-database): A named characteristic describing an entity or relation.
- [Attribute Closure](https://www.ask-codey.com/glossary/attribute-closure): The attributes functionally determined by an attribute set under known dependencies.
- [Cardinality](https://www.ask-codey.com/glossary/cardinality): The number of rows in a relation or the allowed counts in a relationship, depending on context.
- [Cost-Based Optimization](https://www.ask-codey.com/glossary/cost-based-optimization): Choosing a plan by comparing estimated resource costs of alternatives.
- [Cursor](https://www.ask-codey.com/glossary/cursor): Steps through query results one row at a time; usually a last resort.
- [Deadlock](https://www.ask-codey.com/glossary/deadlock-database): A cycle where transactions wait indefinitely for resources held by one another.
- [Deferrable Constraint](https://www.ask-codey.com/glossary/deferrable-constraint): A constraint whose checking may be postponed until transaction completion.
- [Dependency Preservation](https://www.ask-codey.com/glossary/dependency-preservation): A decomposition property allowing original dependencies to be enforced without joining relations.
- [Dirty Read](https://www.ask-codey.com/glossary/dirty-read): Reading a change made by another transaction before that transaction commits.
- [Entity](https://www.ask-codey.com/glossary/entity): A distinguishable thing or concept about which data is stored.
- [Entity-Relationship Model](https://www.ask-codey.com/glossary/entity-relationship-model): A conceptual model describing entities, attributes, and relationships.
- [Exclusive Lock](https://www.ask-codey.com/glossary/exclusive-lock): A lock preventing other transactions from taking conflicting read or write locks.
- [Execution Plan](https://www.ask-codey.com/glossary/execution-plan): The physical operators and access paths used to execute a statement.
- [Fifth Normal Form (5NF)](https://www.ask-codey.com/glossary/fifth-normal-form-5nf): A normal form where every nontrivial join dependency follows from candidate keys.
- [Fourth Normal Form (4NF)](https://www.ask-codey.com/glossary/fourth-normal-form-4nf): BCNF with no nontrivial multivalued dependency unless its determinant is a superkey.
- [Generalization](https://www.ask-codey.com/glossary/generalization): Combining similar entity types into a broader supertype.
- [Hash Join](https://www.ask-codey.com/glossary/hash-join): A join algorithm that builds a hash table for one input and probes it with the other.
- [Identifying Relationship](https://www.ask-codey.com/glossary/identifying-relationship): A relationship where a parent's key contributes to a dependent entity's identity.
- [Index Scan](https://www.ask-codey.com/glossary/index-scan): Reading multiple entries from an index, often across a range or the full index.
- [Index Seek](https://www.ask-codey.com/glossary/index-seek): Using index keys to navigate directly to a matching value or range.
- [Initially Deferred](https://www.ask-codey.com/glossary/initially-deferred): A constraint mode starting each transaction with checking postponed until commit.
- [Initially Immediate](https://www.ask-codey.com/glossary/initially-immediate): A constraint mode starting each transaction with checking performed after each statement.
- [Join Dependency](https://www.ask-codey.com/glossary/join-dependency): A constraint stating that a relation can be reconstructed by joining specified projections.
- [Lock](https://www.ask-codey.com/glossary/lock): A concurrency-control claim restricting conflicting access to a database resource.
- [Lock Granularity](https://www.ask-codey.com/glossary/lock-granularity): The size of the protected resource, such as a row, page, or table.
- [Lossless Decomposition](https://www.ask-codey.com/glossary/lossless-decomposition): Splitting a relation so joining the parts recreates exactly the original relation.
- [Lost Update](https://www.ask-codey.com/glossary/lost-update): A concurrency problem where one write unintentionally overwrites another transaction's write.
- [Merge Join](https://www.ask-codey.com/glossary/merge-join): A join algorithm that advances through inputs ordered by their join keys.
- [Minimal Cover](https://www.ask-codey.com/glossary/minimal-cover): An equivalent, simplified set of functional dependencies with no unnecessary parts.
- [Multivalued Dependency](https://www.ask-codey.com/glossary/multivalued-dependency): A dependency where one attribute set determines independent sets of values for another.
- [Nested Loop Join](https://www.ask-codey.com/glossary/nested-loop-join): A join algorithm that searches the inner input for each qualifying outer row.
- [Non-Repeatable Read](https://www.ask-codey.com/glossary/non-repeatable-read): Getting a different value when rereading a row changed and committed by another transaction.
- [Optionality](https://www.ask-codey.com/glossary/optionality): Whether participation in a relationship is required or optional.
- [Phantom Read](https://www.ask-codey.com/glossary/phantom-read): A repeated predicate query returning added or removed rows due to another committed transaction.
- [Query Optimizer](https://www.ask-codey.com/glossary/query-optimizer): The RDBMS component that chooses a physical strategy for executing a query.
- [Query Plan](https://www.ask-codey.com/glossary/query-plan): A representation of the operations selected or considered for a query.
- [Sargable Predicate](https://www.ask-codey.com/glossary/sargable-predicate): A predicate shaped so an optimizer can use an index search boundary.
- [Selectivity](https://www.ask-codey.com/glossary/selectivity): The fraction of rows expected to satisfy a predicate.
- [Shared Lock](https://www.ask-codey.com/glossary/shared-lock): A lock allowing compatible readers while blocking conflicting writers.
- [Specialization](https://www.ask-codey.com/glossary/specialization): Dividing a broad entity type into narrower subtypes.
- [Statistics](https://www.ask-codey.com/glossary/statistics): Stored summaries of data distribution used to estimate query costs.
- [Table Scan](https://www.ask-codey.com/glossary/table-scan): Reading a table broadly rather than locating rows through a selective index path.
- [Weak Entity](https://www.ask-codey.com/glossary/weak-entity): An entity that depends on another entity for part of its identity.

[Read them in the glossary](https://www.ask-codey.com/glossary/subjects/database/freelancer)

Source: https://www.ask-codey.com/decks/database/freelancer