Oracle 1Z0-084 key terms

The comma-separated set of columns, expressions, or literals that determines which values appear in each row of a query's result set. It is evaluated after row filtering and can include aliases and calculations.

A filter applied to individual rows before any grouping or aggregation occurs. Rows whose condition evaluates to unknown or false are excluded from the result set.

A temporary heading assigned to a column or expression in a query result, used to improve readability. It exists only for the duration of the query and does not rename the underlying column.

A keyword that removes duplicate rows from a result set by comparing all selected column values. It applies to the entire SELECT list, not to a single column.

A symbol or keyword such as =, <, >=, <> or != that compares two expressions and yields true, false, or unknown. It is typically used inside a WHERE or HAVING condition.

A range test that returns true when a value lies inclusively between a lower and an upper bound. It is shorthand for two comparisons combined with AND.

A membership test that returns true when a value matches any item in a supplied list or subquery result. It is equivalent to a chain of equality comparisons joined by OR.

A pattern-matching test for character data using percent and underscore wildcards. An optional ESCAPE clause designates a character that makes a wildcard literal.

A marker meaning a value is absent or unknown rather than zero or blank. Comparisons with NULL yield unknown, so IS NULL and IS NOT NULL must be used to test for it.

The arrangement of query output produced by ORDER BY, ascending by default and descending when DESC is specified. It is applied after the SELECT list is evaluated and can reference aliases.

A function that operates on one row at a time and returns exactly one result per row processed. Character, numeric, date, and conversion functions all fall into this category.

A function that changes a value from one datatype to another, either implicitly or explicitly. TO_CHAR, TO_DATE, and TO_NUMBER are the explicit forms most often tested.

A character pattern that tells a conversion function how to interpret or display date and numeric data. Elements such as YYYY, MM, and DD control the layout of the output.

A conversion function that turns a character string into a DATE value, using a format model when the string does not match the session's default date format.

A conversion function that turns a date or number into a character string according to a format model. Without a format model, dates use the session's default display format.

A function that replaces a NULL with a specified substitute value. It requires both arguments to be type-compatible and returns the first argument when it is not null.

A function that returns the first non-null value among its arguments. Unlike NVL it accepts more than two arguments, and it evaluates from left to right.

A function such as SUM, AVG, COUNT, MIN, or MAX that operates on a set of rows and returns one result per group. Group functions ignore nulls unless COUNT(*) is used.

A clause that partitions result rows into groups so that group functions can be applied to each group. Every non-aggregated column in the SELECT list must appear in it.

A filter applied to groups after aggregation, unlike WHERE which filters rows before grouping. It typically contains group functions in its condition.

A group function that returns the number of rows. COUNT(*) counts all rows including those with nulls, while COUNT(column) skips nulls in that column.

A join that returns only rows where the join condition matches in both tables. Rows without a counterpart in the other table are discarded from the result.

A join that preserves unmatched rows from one or both tables, filling the missing side with nulls. It is written with LEFT, RIGHT, or FULL OUTER JOIN, or the legacy plus operator.

A join that returns the Cartesian product of two tables, pairing every row of one with every row of the other. It is produced by omitting the join condition or using CROSS JOIN.

The predicate that determines which rows from two sources are combined. It usually equates a primary key column with a matching foreign key column.

A join in which a table is combined with itself, requiring two different aliases so each instance can be referenced separately. It is commonly used for hierarchical comparisons within one table.

A SELECT statement nested inside another statement, used to supply values or rows to the outer query. It can return a single value, multiple rows, or multiple columns.

A keyword such as UNION, UNION ALL, INTERSECT, or MINUS that combines the result sets of two queries. Both queries must have matching column counts and compatible datatypes.

A set operator that concatenates two result sets without removing duplicate rows. It is faster than UNION because no duplicate elimination or sorting is performed.

A DML statement that adds new rows to a table, either one row at a time with VALUES or many rows from a subquery. Omitted columns receive their default or null.

A DML statement that changes existing column values in rows matching a WHERE condition. Omitting the condition updates every row in the table.

A DML statement that conditionally inserts or updates rows in a target table based on matching a source. It combines insert and update logic into a single pass.

Statements such as COMMIT, ROLLBACK, and SAVEPOINT that make DML changes permanent, undo them, or mark intermediate points. They determine the boundaries of a logical unit of work.

A DDL statement that defines a new table, its columns, datatypes, and inline or out-of-line constraints. It commits implicitly and stores the definition in the data dictionary.

A rule enforced on table data, such as NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, or CHECK. Constraints can be enabled or disabled and can be deferred within a transaction.

A constraint that requires values in one table to match values in a referenced primary or unique key. It enforces referential integrity between parent and child tables.

A stored query that behaves like a virtual table, exposing selected rows and columns without storing data itself. It can be simple or complex and may be read-only or updatable.

A schema object that generates unique numeric values on demand, typically for populating surrogate keys. Its next and current values are accessed through NEXTVAL and CURRVAL.

An optional schema object that speeds retrieval of rows by providing a fast access path to table data. It is maintained automatically as the underlying table is changed.

An alias for another schema object that lets users reference it without qualifying the owner and object name. It can be private to a schema or public to all users.

A read-only view exposing metadata about database objects, users, and privileges. Static views such as USER_TABLES and dynamic performance views such as V$SESSION are the main families.

A data dictionary view listing the tables owned by the current user, including table name, tablespace, and statistics such as row count. Its ALL_ and DBA_ counterparts broaden the scope.

A right to perform a specific action, granted either at the system level or on a particular object. System privileges allow actions such as CREATE TABLE; object privileges allow actions such as SELECT.

A named collection of privileges that can be granted to users or other roles to simplify administration. Roles can be enabled or disabled within a session.

A statement that gives privileges or roles to a user or role, optionally with the right to pass them on. WITH GRANT OPTION allows the grantee to grant the same privilege further.