Pseudonym: paydirt
Credit: No
Date: 09/05/03
Time: 03:25:14 PM

Question

What do you think would be better to use as a Primary Key: Address, Major, Name or Social Security number? Why?

Answer

Obviously, Social Security number because it is supposed to be unique. Address, Major, and Name are not unique you can have people with those same attributes. This question is simple but its the basis for databases.

Pseudonym: aceone
Credit: No
Date: 09/08/03
Time: 03:25:14 PM

Question

What are the benefits and limitations to RDBMS?

Answer

The benefits of RDBMS are: 1. the system is simple, flexible, and productive. 2. data is easier to understand and communicate with others 3. users do not have to use predefined keys to input information 4. it is more productive because SQL is easier to learn 5. it is easy to create and access data and extend it if needed. The limitations of RDBMS are: 1. do not have enough storage area to handle data such as images, digital and audio video 2. its inadequacy to operate with languages outside of SQL. 3. the requirement that information must be in tables where relationships between entities are defined by values.

Pseudonym: Cherokee
Credit: No
Date: 09/09/03
Time: 08:43:09 PM

Question

How can you tell if a database is created using RDBMS ?

Answer

You can't really, a file is a file! It would need interpreting by a host system/RDBMS package. A DB of 1 table, can actually be a relational database. Having multiple tables isn'r necessarily relational, they may be tables of autoparts, and fruit. Essentially tho' several tables which link together in a meaningful way (like an orders table, a customers table, and a products table) would be viewed as relational.. But the explicit declaration of foreign keys is not necessary, the linkd may only be formed at the time of querying. This isn't a good idea for stability, but can be done

Pseudonym: P-chan
Credit: No
Date: 09/09/03
Time: 08:56:13 PM

Question

True or false: In a relational database system each database must be self-contained in a single table.

Answer

False! One of the important features of a RDBS is that a single database can be spread across several tables. It is the flat-file database that requires each database to be self-contained in a single table.

Pseudonym: Tamagotchi
Credit: No
Date: 09/10/03
Time: 12:03:09 PM

Question

Name at least 3 Restrictions/Conventions for RDBMS.

Answer

1.Each relation must have a unique name. 2.All Columns Must have unique names. 3.All Columns elements must be of the same data type.

Pseudonym: survivor7
Credit: No
Date: 09/10/03
Time: 03:20:19 PM

Question

What is the relation between a field and a tuple.

Answer

The field is the name of the tuple. The tuple is a column in a relational table. We can name a tuple/column "id", which becomes the field name.

Pseudonym: Moglie
Credit: Yes
Date: 09/10/03
Time: 04:31:47 PM

Question

What is a Realtional DBMS? What is a primary Key?

Answer

A database management system that manages data as a collection of tables in which all data relationship are reperesented by common values in related tables. A primary key is an attribute (or conbination of attributes) that uniquely idetifies each row in a relation.

Pseudonym: chilidog
Credit: No
Date: 09/10/03
Time: 09:30:55 PM

Question

What were the major concepts that Codd tried to include in the RDBMS he first developed.

Answer

View a database as a 2-dimensional table. Attempt to automate the functions applied to a database Make all of the physical operations necessary be performed by the DBMS itself. Make it user-friendly

Pseudonym: meno
Credit: No
Date: 09/11/03
Time: 08:24:56 AM

Question

What is an RDBMS foreign key

Answer

a) A combination of keys used to produce uniqueness b) Any field or combination of fields which does not produce a unique value c) Any key or group of keys that can become a super key d) Are used to relate two or more tables (Correct answer)

Pseudonym: Primo
Credit: No
Date: 09/11/03
Time: 08:57:06 AM

Question

All of the following are purposes of RDBMS keys, except? A)Definition of entity relationships. B)Functional dependence. C)Determination. D)Modularization.

Answer

Answer: D Purposes of RDBMS: -Define Entity Relationships (Through the use of Primary/Foreign Keys). -Determination (Knowing the value of a key field means you also know (Determine) the values of the other fields). -Functional Dependence (An attribute is functionally dependent on another if can be determined by that attribute).

Pseudonym: sage1x
Credit: No
Date: 09/11/03
Time: 09:41:30 AM

Question

Why must RDBMS consider database integrity?

Answer

To maintain the wholeness and unity of the database thorough entity integrity in which all entries are unique and no null values are in the primary key fields. Also foreign keys must have a valid or null entry to their corresponding tables to maintain relational integrity.

Pseudonym: sunny
Credit: No
Date: 09/11/03
Time: 02:18:57 PM

Question

What is ‘information rule’ in RDMS?

Answer

All information in a relational database is represented explicitly at the logical level in exactly one way— by values in tables.

Pseudonym: Chango
Credit: No
Date: 09/11/03
Time: 02:43:38 PM

Question

Just what exactly is a relational model, and how is that related to a relational database management system?

Answer

The relational model defines a set of mathematical operations and constraints that can be applied to tables in databases. These comprise a fundamental theory that is provably correct. Relational operations and constraints are used to define business rules (user defined constraints). A DBMS provides mechanisms to support relational operations and constraints for user defined databases and business rules. Because of the rigid separation of physical and logical views and mathematical underpinnings, the relational model offers great power and capability. The optimization possibilities are enormous in contrast to the limited optimization available for 3rd Generation Languages (3GLs) due to their ad-hoc definition. A relational language like SQL is descriptive, specifying the results desired rather how to obtain the results (procedural).

Pseudonym: Rockets
Credit: No
Date: 09/11/03
Time: 03:51:20 PM

Question

What is the basic theory of relational DBMS model based on?

Answer

The relational database model is based firmly in the mathematical theory of relational algebra and calculus.

Pseudonym: ARAZ
Credit: No
Date: 09/11/03
Time: 04:27:27 PM

Question

What is Relational Algebra?

Answer

The theory of database operations is based on set theory; an algebra is a formal structure consisting of sets and operations on those sets. Therefore, relational algebra is a formal system for manipulating relations. It provides a collection of operations to manipulate relations. It supports the notion of a query, or request to retrieve information from a database. Set operations include: Union, Intersection, Difference and Cartesian Product. There are also special database operations, such as: Select, Project, and Join.

Pseudonym: foglive
Credit: No
Date: 09/11/03
Time: 07:09:34 PM

Question

Why is it that RDBMS are very powerful?

Answer

An important feature of relational systems is that a single database can be spread across several tables. This differs from flat-file databases, in which each database is self-contained in a single table.

Pseudonym: pichirilo
Credit: No
Date: 09/11/03
Time: 09:53:29 PM

Question

RDBMS QUESTION Give an example of a simple select statement.

Answer

SELECT STUDENT_ID FROM STUDENT TABLE WHERE FIRST_NAME = 'JUAN';

Pseudonym: EVH
Credit: No
Date: 09/12/03
Time: 10:37:59 AM

Question

A CANDIDATE KEY is any key or group of keys that could become a ________.

Answer

A) SUPER KEY B) PRIMARY KEY C) COMPOSITE KEY D) SECONDARY KEY

Pseudonym: Gotti
Credit: No
Date: 09/12/03
Time: 10:57:53 AM

Question

What is the main difference between Entity Integrity Constraint and Referential Integrity Constraint?

Answer

In Entity Integrity Constraint, no primary key value can be NULL while in Referential Integrity Constraint, the value of a foreign key must match a value of the primary key in the relation to which it refers.

Pseudonym: Rockets
Credit: No
Date: 09/12/03
Time: 01:37:21 PM

Question

What are two most prominent characteristics of a relational DBMS?

Answer

1) Data stored in tables. 2) Relationships between tables.

Pseudonym: barohi
Credit: Yes
Date: 09/12/03
Time: 01:47:36 PM

Question

what is a database key?

Answer

A database key is an attribute utilized to sort or/and identify data.Each table has primary key which uniquely identifies records. Foriegn keys are used to cross reference data between relational tables. For reference and more heplful information: http://databases.about.com/library/glossary/bldef-key.htm

Pseudonym: barohi
Credit: Yes
Date: 09/12/03
Time: 01:49:28 PM

Question

what is a database key?

Answer

A database key is an attribute utilized to sort or/and identify data.Each table has primary key which uniquely identifies records. Foriegn keys are used to cross reference data between relational tables. For reference and more heplful information: http://databases.about.com/library/glossary/bldef-key.htm

Pseudonym: texasholdem
Credit: No
Date: 09/12/03
Time: 01:53:30 PM

Question

Describe the difference between an Inner Join and and Outer Join.

Answer

An inner join selects rows from two tables such that the value in one column of the first table also appears in a certain column of the second table. For an outer join, the result also includes all rows from the first operand ("left outer join", "*="), or the second operand ("right outer join", "=*"), or both ("full outer join", "*=*"). A field in a result row will be null if the corresponding input table did not contain a matching row.

Pseudonym: chessy
Credit: No
Date: 09/12/03
Time: 02:34:33 PM

Question

What is RDBMS?

Answer

A database management system that manages data as a collection of tables in which all data relationships are represented by common values in related tables.

Pseudonym: surfgirl
Credit: No
Date: 09/12/03
Time: 06:21:04 PM

Question

What are the most widely used RDBMS products?

Answer

Oracle, IBM's DB2 and Microsoft's SQL Server.

Pseudonym: Akane
Credit: No
Date: 09/12/03
Time: 08:39:57 PM

Question

What is the difference between the following RDBMS operators: JOIN, UNION, and INTERSECT?

Answer

With a JOIN command you can make a whole new table by using data from two tables that share same column values. The out put will contain only those rows with common values in their join columns. The UNION command will take two separate unrelated tables to produce one table. If you have one table with only one column and unionize it with another table containing one unrelated column, your result will be a table with two columns. The INTERSECT command combines the results of two unrelated queries into a single output. The structure of the tables used must be compatible. Unless ALL is used, only unique records will be included in the results.

Pseudonym: javes
Credit: No
Date: 09/14/03
Time: 09:15:05 PM

Question

What is Relational Integrity?

Answer

In a Relational Model Multiple copies of the items (entities) are avoided, this can be done creating separated tables (ex. Professors, Students, ...) and the tables are linked using Key fields, these keys specify that a record in one table is related to another record in a different table.

Pseudonym: kwu492
Credit: No
Date: 09/14/03
Time: 10:11:53 PM

Question

What is the difference between these two RDMS operators: SELECT and PROJECT?

Answer

The SELECT command is used to gather "all" or "specific values" from a table (hence retrieving the records with that specific value) whereas PROJECT operator produces a list of values for a "selected" attribute such as producing a new table out of an existing table by retriving only the fields (attributes) that we are interested in.

Pseudonym: wito_loko
Credit: Yes
Date: 09/14/03
Time: 10:29:27 PM

Question

Name 3 advantages and 3 disadvantages of the Hierarchical Model in DBMS

Answer

Advantages: 1)Data Integrity 2)Intended to support Large Databases 3) Numerous ‘tried-and-true’ applications Disadvantages: 1)Complex to manage 2)Complex Programming required 3)Programming Requires a complete understanding of the physical database structure (High Cost Database Administrators)

Pseudonym: snoopy
Credit: No
Date: 09/16/03
Time: 09:55:01 PM

Question

What is a composite key?

Answer

A composite key is a combination of keys (Primaries) that produce one unique key.

Pseudonym: Dr.Feelgood
Credit: No
Date: 09/17/03
Time: 02:16:40 PM

Question

Name one of the Advantages of using Keys in RDBMS

Answer

Avoiding Data Redundancy, Avoiding Confussion, Creating Data Dependency, Defining Entity Relations