# Database glossary

217 Database terms, from Novice to Master. Start with the basics or jump to a level.

Updated: September 28, 2026

## Novice

- [ASC](https://www.ask-codey.com/glossary/asc): An ORDER BY direction that sorts from lower values to higher values.
- [CHECK Constraint](https://www.ask-codey.com/glossary/check-constraint): A constraint requiring inserted or updated rows to satisfy a search condition.
- [Column](https://www.ask-codey.com/glossary/column): A named part of a table that holds values from a defined data type or domain.
- [Column Alias](https://www.ask-codey.com/glossary/column-alias): A temporary output name assigned to a selected expression or column.
- [Comparison Predicate](https://www.ask-codey.com/glossary/comparison-predicate): A condition comparing values with operators such as =, <>, <, or >=.
- [Constraint](https://www.ask-codey.com/glossary/constraint): A rule the database enforces to protect valid and consistent data.
- [Data Type](https://www.ask-codey.com/glossary/data-type-database): A rule defining which values a column or expression may contain and which operations apply.
- [Database](https://www.ask-codey.com/glossary/database): An organized collection of data that software can store, retrieve, and update.
- [DEFAULT Clause](https://www.ask-codey.com/glossary/default-clause): A clause providing a value when an INSERT omits the column.
- [DESC](https://www.ask-codey.com/glossary/desc): An ORDER BY direction that sorts from higher values to lower values.
- [DISTINCT](https://www.ask-codey.com/glossary/distinct): A SELECT option that removes duplicate rows from a result.
- [Domain](https://www.ask-codey.com/glossary/domain): A permitted set of values from which an attribute draws its data.
- [Foreign Key](https://www.ask-codey.com/glossary/foreign-key): Columns whose values must match a referenced unique or primary key, subject to NULL rules.
- [FROM](https://www.ask-codey.com/glossary/from): A query clause identifying the source tables, views, or derived tables.
- [Key](https://www.ask-codey.com/glossary/key): One or more attributes used to identify rows or connect related relations.
- [Logical Predicate](https://www.ask-codey.com/glossary/logical-predicate): A condition that combines or reverses other conditions with AND, OR, or NOT.
- [Many-to-Many Relationship](https://www.ask-codey.com/glossary/many-to-many-relationship): A relationship where rows on both sides can relate to many rows on the other side.
- [NOT NULL Constraint](https://www.ask-codey.com/glossary/not-null-constraint): A constraint requiring a column to contain a non-NULL value.
- [NULL](https://www.ask-codey.com/glossary/null-database): A marker indicating that a value is missing or unknown, rather than zero or an empty string.
- [Numeric Literal](https://www.ask-codey.com/glossary/numeric-literal): A number written directly in a SQL statement.
- [One-to-Many Relationship](https://www.ask-codey.com/glossary/one-to-many-relationship): A relationship where one parent row can relate to many child rows.
- [One-to-One Relationship](https://www.ask-codey.com/glossary/one-to-one-relationship): A relationship where each row can relate to at most one row on the other side.
- [ORDER BY](https://www.ask-codey.com/glossary/order-by): A clause that sorts a query result by one or more expressions.
- [Primary Key](https://www.ask-codey.com/glossary/primary-key): The chosen candidate key that uniquely identifies every row and cannot contain NULL.
- [Query](https://www.ask-codey.com/glossary/query): A request for data or another result from a database.
- [Relation](https://www.ask-codey.com/glossary/relation): A set of tuples sharing the same named attributes in the relational model.
- [Relational Database](https://www.ask-codey.com/glossary/relational-database): A database that represents data as relations commonly presented as tables.
- [Relational Database Management System (RDBMS)](https://www.ask-codey.com/glossary/relational-database-management-system-rdbms): Software that creates, protects, queries, and updates relational databases.
- [Relationship](https://www.ask-codey.com/glossary/relationship): A meaningful association between entities represented through keys and relations.
- [Result Set](https://www.ask-codey.com/glossary/result-set): The rows and columns produced by a query.
- [Row](https://www.ask-codey.com/glossary/row): One record in a table containing a value for each column.
- [Schema](https://www.ask-codey.com/glossary/schema): The named structure defining database objects such as tables, views, and constraints.
- [SELECT](https://www.ask-codey.com/glossary/select-database): A statement or query clause that chooses expressions and columns for a result.
- [Snake Case](https://www.ask-codey.com/glossary/snake-case): All letters are lower case, each word is separated by an underscore.
- [SQL Statement](https://www.ask-codey.com/glossary/sql-statement): A complete SQL instruction sent to a database management system.
- [String Literal](https://www.ask-codey.com/glossary/string-literal): Text written between single quotation marks in SQL.
- [Structured Query Language (SQL)](https://www.ask-codey.com/glossary/structured-query-language-sql): The standardized language for defining, querying, and changing relational data.
- [Table](https://www.ask-codey.com/glossary/table): The common SQL representation of a relation, arranged in rows and columns.
- [UNIQUE Constraint](https://www.ask-codey.com/glossary/unique-constraint): A constraint preventing duplicate values or value combinations in specified columns.
- [Unique Key](https://www.ask-codey.com/glossary/unique-key): One or more columns constrained so duplicate combinations are not allowed.
- [WHERE](https://www.ask-codey.com/glossary/where-database): A query clause keeping only rows for which its condition is true.

## Apprentice

- [Aggregate Function](https://www.ask-codey.com/glossary/aggregate-function): A function that summarizes a set of rows into one value.
- [ALTER TABLE](https://www.ask-codey.com/glossary/alter-table): A statement that changes the definition of an existing table.
- [Approximate Numeric Type](https://www.ask-codey.com/glossary/approximate-numeric-type): A floating-point numeric type that may store an approximation of a value.
- [AVG](https://www.ask-codey.com/glossary/avg): An aggregate function returning the average of non-NULL numeric values.
- [BETWEEN Predicate](https://www.ask-codey.com/glossary/between-predicate): A predicate testing whether a value falls within an inclusive lower and upper bound.
- [CASE Expression](https://www.ask-codey.com/glossary/case-expression): An expression that chooses a result by evaluating conditions in order.
- [Character String Type](https://www.ask-codey.com/glossary/character-string-type): A SQL type whose values are sequences of characters.
- [COUNT](https://www.ask-codey.com/glossary/count): An aggregate function returning the number of qualifying rows or non-NULL expression values.
- [CREATE TABLE](https://www.ask-codey.com/glossary/create-table): A statement that defines a new table, its columns, and its constraints.
- [CREATE VIEW](https://www.ask-codey.com/glossary/create-view): A statement that defines a view from a query.
- [CROSS JOIN](https://www.ask-codey.com/glossary/cross-join): A join returning every possible pairing of rows from two table expressions.
- [Data Control Language (DCL)](https://www.ask-codey.com/glossary/data-control-language-dcl): SQL statements that control database privileges and access.
- [Data Definition Language (DDL)](https://www.ask-codey.com/glossary/data-definition-language-ddl): SQL statements that define or change database structures.
- [Data Manipulation Language (DML)](https://www.ask-codey.com/glossary/data-manipulation-language-dml): SQL statements that retrieve or change stored rows.
- [Date and Time Type](https://www.ask-codey.com/glossary/date-and-time-type): A SQL type representing a date, time, timestamp, or interval.
- [DELETE](https://www.ask-codey.com/glossary/delete): A statement that removes selected rows from a table.
- [DROP TABLE](https://www.ask-codey.com/glossary/drop-table): A statement that removes a table definition and its stored data.
- [Exact Numeric Type](https://www.ask-codey.com/glossary/exact-numeric-type): A numeric type representing values with defined precision and scale without binary approximation.
- [EXCEPT](https://www.ask-codey.com/glossary/except): A set operation returning distinct rows in the first result but not the second.
- [EXISTS Predicate](https://www.ask-codey.com/glossary/exists-predicate): A predicate that is true when its subquery returns at least one row.
- [FETCH FIRST](https://www.ask-codey.com/glossary/fetch-first): A standard clause limiting a query result to its first specified number of rows.
- [FULL OUTER JOIN](https://www.ask-codey.com/glossary/full-outer-join): A join returning matched rows plus unmatched rows from both sides.
- [GROUP BY](https://www.ask-codey.com/glossary/group-by): A clause collecting rows with equal grouping values so each group produces one result row.
- [HAVING](https://www.ask-codey.com/glossary/having): A clause filtering groups after grouping and aggregation.
- [IN Predicate](https://www.ask-codey.com/glossary/in-predicate): A predicate testing whether a value equals any value in a list or subquery result.
- [INNER JOIN](https://www.ask-codey.com/glossary/inner-join): A join returning only row combinations that satisfy its join condition.
- [INSERT](https://www.ask-codey.com/glossary/insert): A statement that adds new rows to a table.
- [INTERSECT](https://www.ask-codey.com/glossary/intersect): A set operation returning distinct rows present in both query results.
- [IS NULL Predicate](https://www.ask-codey.com/glossary/is-null-predicate): A predicate testing whether a value is NULL.
- [JOIN](https://www.ask-codey.com/glossary/join-database): A query operation combining related rows from two table expressions.
- [Join Condition](https://www.ask-codey.com/glossary/join-condition): The predicate deciding which rows from joined sources match.
- [LEFT OUTER JOIN](https://www.ask-codey.com/glossary/left-outer-join): A join returning every left row and matching right rows, using NULLs when no right match exists.
- [LIKE Predicate](https://www.ask-codey.com/glossary/like-predicate): A predicate comparing text with a pattern containing wildcard characters.
- [MAX](https://www.ask-codey.com/glossary/max): An aggregate function returning the highest non-NULL value.
- [MIN](https://www.ask-codey.com/glossary/min): An aggregate function returning the lowest non-NULL value.
- [OFFSET Clause](https://www.ask-codey.com/glossary/offset-clause): A clause skipping a specified number of ordered result rows.
- [ON Clause](https://www.ask-codey.com/glossary/on-clause): A join clause containing its match condition.
- [RIGHT OUTER JOIN](https://www.ask-codey.com/glossary/right-outer-join): A join returning every right row and matching left rows, using NULLs when no left match exists.
- [Scalar Subquery](https://www.ask-codey.com/glossary/scalar-subquery): A subquery required to return one column and no more than one row.
- [Self Join](https://www.ask-codey.com/glossary/self-join): A query that joins a table to another reference to the same table.
- [SET Clause](https://www.ask-codey.com/glossary/set-clause): The UPDATE clause assigning new values to columns.
- [Set Operation](https://www.ask-codey.com/glossary/set-operation): An operation combining compatible query results according to set rules.
- [Subquery](https://www.ask-codey.com/glossary/subquery): A query nested inside another SQL statement.
- [SUM](https://www.ask-codey.com/glossary/sum-database): An aggregate function adding the non-NULL numeric values in a group.
- [Table Subquery](https://www.ask-codey.com/glossary/table-subquery): A subquery producing rows and columns that another query can use as a table.
- [Transaction Control Language (TCL)](https://www.ask-codey.com/glossary/transaction-control-language-tcl): SQL statements that complete, reverse, or mark points within transactions.
- [UNION](https://www.ask-codey.com/glossary/union): A set operation combining compatible query results and removing duplicate rows.
- [UNION ALL](https://www.ask-codey.com/glossary/union-all): A set operation combining compatible query results while retaining duplicate rows.
- [UPDATE](https://www.ask-codey.com/glossary/update): A statement that changes values in existing rows.
- [VALUES Clause](https://www.ask-codey.com/glossary/values-clause): A clause that supplies rows of literal or calculated values.
- [View](https://www.ask-codey.com/glossary/view): A named query whose result can be used much like a table.
- [Wildcard Character](https://www.ask-codey.com/glossary/wildcard-character): A pattern character representing unknown text, such as % or \_ with LIKE.

## Journeyman

- [ACID Compliance](https://www.ask-codey.com/glossary/acid-compliance): Atomic, Consistent, Isolated, Durable
- [ACID Properties](https://www.ask-codey.com/glossary/acid-properties): Atomicity, consistency, isolation, and durability: four goals for reliable transactions.
- [Alternate Key](https://www.ask-codey.com/glossary/alternate-key): A candidate key not selected as the primary key.
- [Associative Entity](https://www.ask-codey.com/glossary/associative-entity): An entity representing a relationship and optionally storing attributes about that relationship.
- [Atomicity](https://www.ask-codey.com/glossary/atomicity): The property that all work in a transaction succeeds together or none of it takes effect.
- [Boyce-Codd Normal Form (BCNF)](https://www.ask-codey.com/glossary/boyce-codd-normal-form-bcnf): A normal form requiring every determinant of a nontrivial dependency to be a superkey.
- [Candidate Key](https://www.ask-codey.com/glossary/candidate-key): A minimal set of attributes that uniquely identifies every tuple in a relation.
- [Clustered Index](https://www.ask-codey.com/glossary/clustered-index): The index that decides the order rows are stored in; one per table.
- [COMMIT](https://www.ask-codey.com/glossary/commit): A statement that successfully ends a transaction and makes its changes durable.
- [Common Table Expression (CTE)](https://www.ask-codey.com/glossary/common-table-expression-cte): A named query expression introduced by WITH for use within one statement.
- [Composite Key](https://www.ask-codey.com/glossary/composite-key): A key made from two or more attributes.
- [Consistency](https://www.ask-codey.com/glossary/consistency): The property that a successful transaction preserves declared database rules.
- [Correlated Subquery](https://www.ask-codey.com/glossary/correlated-subquery): A subquery that refers to values from an outer query and is evaluated in that context.
- [Delete Anomaly](https://www.ask-codey.com/glossary/delete-anomaly): A design problem where deleting one fact unintentionally removes another fact.
- [Denormalization](https://www.ask-codey.com/glossary/denormalization): Deliberately adding controlled redundancy to support a measured performance or reporting need.
- [DENSE_RANK](https://www.ask-codey.com/glossary/dense-rank): A window function assigning equal rank to peers without leaving gaps after ties.
- [Determinant](https://www.ask-codey.com/glossary/determinant): The attribute set on the left side of a functional dependency.
- [Durability](https://www.ask-codey.com/glossary/durability): The property that committed changes survive a later failure.
- [Entity Integrity](https://www.ask-codey.com/glossary/entity-integrity): The rule that every relation has a primary key whose values are unique and non-NULL.
- [First Normal Form (1NF)](https://www.ask-codey.com/glossary/first-normal-form-1nf): The normal form requiring each attribute value to be a single value from its domain.
- [Functional Dependency](https://www.ask-codey.com/glossary/functional-dependency): A rule where one set of attributes determines another set of attributes.
- [Index](https://www.ask-codey.com/glossary/index): An auxiliary data structure that helps an RDBMS locate rows without scanning every row.
- [Insert Anomaly](https://www.ask-codey.com/glossary/insert-anomaly): A design problem where one fact cannot be stored without supplying an unrelated fact.
- [Isolation](https://www.ask-codey.com/glossary/isolation): The property controlling how concurrent transactions can observe one another's work.
- [Junction Table](https://www.ask-codey.com/glossary/junction-table): A table that represents a many-to-many relationship through foreign keys.
- [LAG](https://www.ask-codey.com/glossary/lag): A window function returning a value from an earlier row in the window partition.
- [LEAD](https://www.ask-codey.com/glossary/lead): A window function returning a value from a later row in the window partition.
- [Natural Key](https://www.ask-codey.com/glossary/natural-key): A key formed from meaningful values that already belong to the modeled domain.
- [Nonclustered Index](https://www.ask-codey.com/glossary/nonclustered-index): A separate sorted lookup structure that points back to the rows.
- [Normalization](https://www.ask-codey.com/glossary/normalization): Organizing relations to reduce redundancy and prevent modification anomalies.
- [OVER Clause](https://www.ask-codey.com/glossary/over-clause): The clause defining the row window used by a window function.
- [Parameterized Query](https://www.ask-codey.com/glossary/parameterized-query): A query keeping data values separate from SQL text through parameters.
- [PARTITION BY](https://www.ask-codey.com/glossary/partition-by): An OVER subclause dividing query rows into independent window-function groups.
- [Prepared Statement](https://www.ask-codey.com/glossary/prepared-statement): A parsed statement template executed later with supplied parameter values.
- [RANK](https://www.ask-codey.com/glossary/rank): A window function assigning equal rank to peers and leaving gaps after ties.
- [READ COMMITTED](https://www.ask-codey.com/glossary/read-committed): An isolation level preventing a statement from reading uncommitted changes.
- [READ UNCOMMITTED](https://www.ask-codey.com/glossary/read-uncommitted): The isolation level allowing the broadest concurrency and permitting dirty reads.
- [Recursive CTE](https://www.ask-codey.com/glossary/recursive-cte): A CTE that repeatedly refers to its own accumulated result until no new rows are produced.
- [Referential Integrity](https://www.ask-codey.com/glossary/referential-integrity): The rule that foreign-key values must reference an existing allowed key or be NULL when permitted.
- [REPEATABLE READ](https://www.ask-codey.com/glossary/repeatable-read): An isolation level preventing reread rows from changing during the transaction.
- [ROLLBACK](https://www.ask-codey.com/glossary/rollback): A statement that reverses a transaction's uncommitted changes.
- [ROW_NUMBER](https://www.ask-codey.com/glossary/row-number): A window function assigning consecutive numbers to rows within each window partition.
- [SAVEPOINT](https://www.ask-codey.com/glossary/savepoint): A named point inside a transaction to which later work can be rolled back.
- [Second Normal Form (2NF)](https://www.ask-codey.com/glossary/second-normal-form-2nf): First normal form with no non-key attribute dependent on only part of a candidate key.
- [SERIALIZABLE](https://www.ask-codey.com/glossary/serializable): The strongest standard isolation level, requiring results consistent with some serial order.
- [SQL Injection](https://www.ask-codey.com/glossary/sql-injection): A vulnerability where untrusted input changes the intended structure of a SQL statement.
- [Stored Procedure](https://www.ask-codey.com/glossary/stored-procedure): A named, saved set of SQL statements with parameters.
- [Superkey](https://www.ask-codey.com/glossary/superkey): Any attribute set that uniquely identifies every tuple, including sets with unnecessary attributes.
- [Surrogate Key](https://www.ask-codey.com/glossary/surrogate-key): A key introduced solely to identify rows and carrying no domain meaning.
- [Third Normal Form (3NF)](https://www.ask-codey.com/glossary/third-normal-form-3nf): Second normal form with non-key attributes depending on keys rather than other non-key attributes.
- [Transaction](https://www.ask-codey.com/glossary/transaction): A logical unit of database work completed or reversed as a whole.
- [Transaction Isolation Level](https://www.ask-codey.com/glossary/transaction-isolation-level): A setting defining which effects of concurrent transactions may be observed.
- [Trigger](https://www.ask-codey.com/glossary/trigger): Code that runs automatically when a table's rows change.
- [Unique Index](https://www.ask-codey.com/glossary/unique-index): An index that also prevents duplicate indexed value combinations.
- [Update Anomaly](https://www.ask-codey.com/glossary/update-anomaly): A design problem where repeated copies of one fact can become inconsistent during an update.
- [Window Frame](https://www.ask-codey.com/glossary/window-frame): The subset of rows around the current row used by a window function.
- [Window Function](https://www.ask-codey.com/glossary/window-function): A function calculating across related rows without collapsing them into one row per group.

## Freelancer

- [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.

## Master

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

[More subjects in Databases](https://www.ask-codey.com/glossary/groups/databases)

Source: https://www.ask-codey.com/glossary/subjects/database