Oracle 1Z0-182 key terms

A way of storing data as tables of rows and columns, where each row is a distinct record and relationships between tables are expressed by matching key values rather than by physical links.

A column or set of columns whose values uniquely identify each row in a table; it must be unique and cannot contain nulls, and each table may have only one.

A column or set of columns whose values must match a primary or unique key value in another table, or be null, thereby enforcing referential integrity between parent and child tables.

A marker meaning a value is unknown, missing, or not applicable. It is not zero or a blank string, and any arithmetic or comparison with it yields unknown unless handled explicitly.

The condition evaluation rule in SQL where a comparison returns TRUE, FALSE, or UNKNOWN; rows are returned only when the condition is TRUE, so NULL comparisons are excluded.

The attribute that defines what kind of values a column may hold and how much storage it uses, such as character, numeric, date-time, or large object types.

A variable-length character type declared with a maximum length, either in bytes or characters; Oracle stores only the actual characters entered, up to that limit.

The SQL statement that retrieves rows from one or more tables or views, consisting of clauses such as SELECT, FROM, WHERE, GROUP BY, HAVING, and ORDER BY.

The optional clause that filters rows before any grouping occurs, keeping only rows for which the specified condition evaluates to TRUE.

The clause that sorts the final result set by one or more expressions, each optionally ascending or descending; it is applied last, after filtering and grouping.

The FETCH FIRST n ROWS ONLY syntax, optionally with OFFSET, that restricts how many rows a query returns after sorting, replacing older techniques based on ROWNUM.

A number assigned to a row as it is produced by a query, starting at 1; because it is applied before sorting, filtering on it can give unexpected results.

A pattern-matching condition using percent as a wildcard for any string and underscore for exactly one character; an escape character can make wildcards literal.

The only correct way to test for a missing value, written as column IS NULL or IS NOT NULL, because equality comparison with null returns unknown rather than true.

A function that operates on one row at a time and returns one result per row, such as character, numeric, date, or conversion functions used in SELECT and WHERE.

A function such as SUM, AVG, COUNT, MIN, or MAX that operates on a set of rows and returns a single aggregated result, ignoring nulls except in COUNT of a column.

The clause that collects rows into groups sharing the same values in the listed expressions so that group functions can be applied to each group separately.

The clause that filters groups after aggregation, unlike WHERE which filters individual rows; it may reference group functions that are not allowed in WHERE.

A single-row function that substitutes a replacement value when its first argument is null, allowing arithmetic or concatenation to produce meaningful results.

Automatic translation of a value from one data type to another performed by Oracle, which can silently disable index use and cause errors when formats do not match.

Converting a value deliberately with functions such as TO_CHAR, TO_NUMBER, or TO_DATE, giving predictable results and a format model when needed.

A join that returns only row combinations satisfying the join condition, discarding rows from either table that have no matching partner.

A join that preserves unmatched rows from one or both tables, filling the other side's columns with nulls; variants are LEFT, RIGHT, and FULL.

The predicate that determines which rows from two row sources are combined, usually an equality between a foreign key and a primary key.

A SELECT statement nested inside another statement, usable in the WHERE, FROM, or SELECT clause to supply values or act as an inline view.

A subquery that references a column from the outer query, so it is re-evaluated for each outer row rather than once for the whole statement.

The statement that adds new rows to a table, either one row with a VALUES clause or many rows by selecting from another row source.

The statement that changes existing column values in rows matching a WHERE condition; omitting the condition modifies every row in the table.

The statement that removes rows matching a WHERE condition from a table while leaving the table structure intact; omitting the condition removes all rows.

A single statement that conditionally inserts new rows and updates existing ones by comparing a source row set with a target table on a join condition.

The DDL statement that defines a new table, its columns, data types, default values, and inline or out-of-line constraints.

A rule attached to a table that restricts the data it may contain, such as NOT NULL, unique, primary key, foreign key, or check constraints.

A rule, implemented by a foreign key, that prevents orphan child rows and can specify what happens to children when the parent row is deleted.

A foreign key option that automatically deletes dependent child rows when the referenced parent row is deleted, instead of blocking the delete.

A stored query that behaves like a virtual table; it contains no data of its own and can restrict columns or rows exposed to users.

A schema object that generates successive numeric values on request, commonly used to populate surrogate primary keys without locking a table.

An alternative name for a schema object that lets users reference it without qualifying the owner, and can be private or public.

An optional schema object that provides a fast access path to rows based on key values, maintained automatically by Oracle as data changes.

The collection of database objects owned by a single user account; the schema name is the same as the user name and objects are referenced with it as a prefix.

The statement that gives a user or role a system privilege or an object privilege, optionally with the right to pass that privilege on.

A named group of privileges that can be granted to users, simplifying administration because privileges are managed in one place.

A logical unit of work consisting of one or more DML statements that is made permanent by COMMIT or undone by ROLLBACK as a whole.

The statement that ends a transaction by making all its changes permanent and visible to other sessions, and releases locks held by the session.

The statement that ends a transaction by undoing all changes made since the last commit, returning the data to its prior state.