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DBM Cheat Sheet by

dbm

Defi­nitions 1

 
Gene­ral­iza­tion - the process of defining a more general entity type from a set of more specia­lized entity types
Weak Entity type - an entity type whose existence depends on another entity type a
Comp­osite Key - is a set of more than one key that, together, uniquely identifies each record.
Foreign Key - is a key in some table which uniquely identifies rows in another table
The entity integrity rule - The primary key for a row is unique, and any primary key is not null

Primary Key

Primary Key

Composite Key

CompKey

Defi­nitions Contin­ued

 
Refe­rential Integrity Constr­aint - each foreign key value must match a primary key value in the other relation
Meta­-Data - Data that describes the properties of other data - ex. (rules or constr­ain­ts,data defini­tions and struct­ures)
CASE - a class of tools that automates the design of databases and applic­ation programs.
Inse­rtion anomaly - when certain attributes cannot be inserted into the database without the presence of other attributes

Insertion

Insert Anomaly

**True­/False

 
1. Metadata are data that describe the properties of other data - True
2. Redundancy increases the risk of incons­istent data - True
3. Cost and complexity are just two of the disadv­antages of database processing - True
4. In an E-R diagram, strong entities are repres­ented by double­-walled rectangles - False
5. In an E-R diagram, an associ­ative entity is repres­ented by a rounded rectangle - True
6. A single occurrence of an entity is called an entity instance - True
 

True/False

 
7. An entity type name should always be a singular noun - True
8. A multiv­alued attribute may take on more than one value for a particular entity instance - True
9. A cardin­ality constraint tells what kinds of properties are associated with an entity - False
10. A member of a subtype does NOT necess­arily have to be a member of the supertype - False
11. There are three separate discri­min­ators in the following diagram because of the overlap rule - True

Deletion Anomaly

Deletion

True/False

 
13. A composite key consists of only one attribute - False
14. A primary key is an attribute that uniquely identifies each row in a relation - True
15. The following figure is an example of total specia­liz­ation - False
16. A foreign key is a primary key of a relation that also is a primary key in another relation - False
17. One property of a relation is that each attribute within a relation has a unique name - True

Defi­nitions 3

 
Deletion anomaly - exists when certain attributes are lost because of the deletion of other attributes
When a regular entity type contains a multiv­alued attribute, one must - create two new relations, one containing the multiv­alued attribute
Tran­sitive Depend­ency - A functional dependency between two or more non-key attributes
Total Specia­liz­ation - specifies that for each entity instance of the supertype must be a member of some subtype in the relati­onship

True/False

 
18. There can be multiv­alued attributes in a relation - False
19. Unlike columns, the rows of a relation may not be interc­hanged and must be stored in one sequence - False
20. The allowable range of values for a given attribute is part of the domain constraint - True
21. A cascading delete removes all records in other tables associated with the record to be deleted - True
22. When transf­orming a one-to-one relati­onship, a new relation is always created - False
 

Modifi­cation Anomaly

Mod

Transitive Specia­liz­ation

Trans

Partial Specia­liz­ation

Part Spec

Total Specia­liz­ation

Total

Misc

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