Chapter 7

Schema

A group of database objects, such as tables and indexes, that are related to each other.

Cascading Order Sequence

A multilevel ordered sequence that can be created easily by listing several attributes, separated by commas, after the ORDER BY clause.

Sub/Nested/Inner Query

A query that is embedded inside another query. The inner query is always executed first by the RDBMS.

Boolean Algebra

A specialty field in mathematics that is dedicated to the use of logical operators.

Recursive Query

A table that must be joined to itself.

View

A virtual table based on a SELECT query. The query can contain columns, computed columns, aliases, and aggregate functions from one or more tables.

Alias

An alternative name given to a column or table in any SQL statement.

DROP TABLE

Is how you permanently delete a table!!!!!

Non PK or FK constraint

NOT NULL --> ensures that a column doesn't accept nulls UNIQUE--> ensures that all values in a column are unique DEFAULT--> assigns a value to an attribute when a new row is added to a table. CHECK--> used to validate data when an attribute is entered. Checks to see if a specific condition exists.

Nested Query: Inner Query

Part of a nested query that is executed first

Nested Query: Outer Query

Part of a nested query that is executed last (but its always the first SQL command you encounter).

Rules of Precedence

Rules that establish the order in which computations are completed.

Data Definition Language (DDL)

SQL includes commands to create database objects such as tables, indexes, and views, as well as commands to define access rights to those database objects.

Data Manipulation Language (DML)

SQL includes commands to insert, update, delete, and retrieve data within the database tables.

Wildcard Character

Symbol that can be used as a general substitue for other characters or commands.

Authentication

The process through which the DBMS verifies that only registered users may access the database. To be authenticated, you must log on to the RDBMS using a user ID and a password created by the database administrator.

Base Tables

The tables on which the view is based.

Reserved Words

Words used by SQL to perform specific functions. For example, in some RDBMSs, the column name INITIAL will generate the message invalid column name.