PT2520 Week 5 Assignments 1
Week 5 Assignment 1
January 28, 2015
Database Concepts
James Johnson (17991808)
Mrs. Hubbard
1. Define the term “physical design” with regard to databases.
Database design adapted to the features and limitations of a particular RDBMS.
2. What is a database transaction?
- Any action that a database takes, creating objects, adding rows, changing data in rows, removing rows, and so on.
3. What is Unicode?
An expanded character set that includes non-Latin character sets such as Russian or Japanese.
4. What is a datatype?
The column specification that determines what kind of data can be stored in that column, character versus numeric or date, for example.
5. Give an example of a variable character type.
Data type :Varchar
Description: Variable-length ASC II. Example: “ Los Angeles,” maximum 255 characters unless MAX (MAX allows 2^31 – 1 bytes)
6. Define the term null.
A null represents the absence of a value. A null value is unknown.
7. What is referential integrity? How does it affect insert, delete and update transactions?
Referential Integrity exists when every foreign key relates to an existing primary key. There are no orphan records in child tables that have no reference in a parent table.
Inserts enter new data into the database.
Updates change existing data.
Deletes remove rows of data from the database.
8. When should you allow nulls in designing a table? When should you not allow nulls when designing a table?
If you allow nulls, you can leave that column blank when you are entering data.
If you do not allow nulls, you must enter a value into the column to continue.
9. What SQL statement would you use to make a table in SQL?
Creating tables in the graphical interface is not the only way to create a table. It is also possible to create the table using the SQL programming language.
CREATE TABLE Course
(
CourseKey NCHAR( 10) PRIMARY KEY, CourseName NVARCHAR( 50) NOT NULL, CourseDescription NVARCHAR( 200) NULL
)
January 28, 2015
Database Concepts
James Johnson (17991808)
Mrs. Hubbard
1. Define the term “physical design” with regard to databases.
Database design adapted to the features and limitations of a particular RDBMS.
2. What is a database transaction?
- Any action that a database takes, creating objects, adding rows, changing data in rows, removing rows, and so on.
3. What is Unicode?
An expanded character set that includes non-Latin character sets such as Russian or Japanese.
4. What is a datatype?
The column specification that determines what kind of data can be stored in that column, character versus numeric or date, for example.
5. Give an example of a variable character type.
Data type :Varchar
Description: Variable-length ASC II. Example: “ Los Angeles,” maximum 255 characters unless MAX (MAX allows 2^31 – 1 bytes)
6. Define the term null.
A null represents the absence of a value. A null value is unknown.
7. What is referential integrity? How does it affect insert, delete and update transactions?
Referential Integrity exists when every foreign key relates to an existing primary key. There are no orphan records in child tables that have no reference in a parent table.
Inserts enter new data into the database.
Updates change existing data.
Deletes remove rows of data from the database.
8. When should you allow nulls in designing a table? When should you not allow nulls when designing a table?
If you allow nulls, you can leave that column blank when you are entering data.
If you do not allow nulls, you must enter a value into the column to continue.
9. What SQL statement would you use to make a table in SQL?
Creating tables in the graphical interface is not the only way to create a table. It is also possible to create the table using the SQL programming language.
CREATE TABLE Course
(
CourseKey NCHAR( 10) PRIMARY KEY, CourseName NVARCHAR( 50) NOT NULL, CourseDescription NVARCHAR( 200) NULL
)