CH4 - Relational Databases

The constraint that all foreign keys must have either null values or the value of a primary key in another table is referred to as which of the following? a. referential integrity rule b. entity integrity rule c. foreign key value rule d. null value rule

Referential integiry rule

What is an internal schema?

a low level view of the database including record layouts, addresses, and indexes

Basic reqs of a relational database: 1. Every column in a row must be single valued 2. Primary keys cannot be null 3. Foreign keys, if not null, must have values that correspond to the value of a primary key in another table 4. All nonkey attributes in a table must describe a characteristic of the object identified by the primary key

1. Every column in a row must be single valued 2. Primary keys cannot be null 3. Foreign keys, if not null, must have values that correspond to the value of a primary key in another table 4. All nonkey attributes in a table must describe a characteristic of the object identified by the primary key

What is each row in a relational database table called?

A tuple

Which would be a file? Customers name Data about one customer All inventory records Data about one inventory item

All inventory records

What is the external schema?

An individual users view of portions of the database

Which of the following attributes in the Cash Receipts table (representing payments received from customers) would most likely be a foreign key? a. cash receipt number b. customer check number c. customer number d. cash receipt date

Customer number

Difference of DDHl, DML and DQL?

DDL builds the data dictionary and creates views for each user DML changes database content and manipulates data DQL is a high level, english language which allows easy commends to be used to manipulate data

A database tech benefit that makes it easier for information to be combined in unlimited ways is: Data sharing Data independence Central Management Data Integration

Data integration

The constraint that all primary keys must have nonnull data values is referred to as which of the following? a. referential integrity rule b. entity integrity rule c. normalization rule d. relational data model rule

Entity integiry rule

Customer name would be considered a: Field File Record Database

Field

The data that shows how the user or programmer conceptually organizes and understands the data is the Record view Logical View Physical View None

Logical

What is normalization? What is semantic modeling?

Normalization is when everything is intitially stored in one large table and then rules are followed to decompose it into several well connected tabled (3nf) Semantic modeling is when the database is made already in 3nf form

What is a primary key? What is a foreign key?

Primary key: A database attribute which uniquely identifies a specific row or table Foreign key: An attribute in a table that is also a primary key in another table and is used to link two tables

What is the conceptual schema

The organization wide view of the entire database, lists all elements and relationships