discreat presentation data

8/9/2019 Discreat Presentation Data

1/5

There are several types of cardinality defining relationships between occurrences ofentities on two sides of the line of relationships.

The Link Cardinality is a 0:0 relationship and defined as one side does not need theother to exists. For example, in a person and parking space relationship, it denotes

that I do not need to have a person to have a parking space and I dont need aparking space to have a person either. It also denotes that a person can only occupyone parking space. This relation need to have one entity nominated to become thedominant table and use programs or triggers to limit the number of related recordsstored inside the other table in the relation.

The Sub-type Cardinality is a 1:0 relationship and defined as having one optionalside only. An example would be a person and programmer relation. This is a 1:0relation meaning that a person can be a programmer but a programmer must alwaysbe a person. The mandatory side of the relation, in the case the programmer side, isdominant in the relationship. Triggers and programs are again used in the controllingthe database.

The Physical Segment Cardinality is 1:1 relationship and it is demonstrated thatboth sides of the relationship are mandatory. Example may be a person and DNApatters. This relationship show that a person must only have one set of DNA patternswhile the DNA patters as dictated by nature can only be applied on one person.

The Possession Cardinality is a 0:M relation (zero to many) relationship on bothsides. For example, a person may own no phone or maybe plenty of phones but aphone may have no owner but has a potential to be owned by a person. In databaseimplementation, a nullable foreign key column in the phone table is used to

reference the person in its table.

The Child Cardinality is a 1:M mandatory relationship and is one of the mostcommon relationships used most databases. An example would be a person tableand membership table relationship. This relationship denotes that a person can be amember or not but a person can also be a member of many organizations. Theforeign key in the membership table has to be mandatory and not null.

The Characteristic Cardinality is a 0:M relationship which is mandatory on bothsides. An example would be a person and name table relationship. This denotes that

a person should have at least one name but may also many names. The databaseimplantation for this cardinality involves a nullable foreign key in the name table tothe person table.

The Paradox Cardinality is 1:M relationship which is mandatory to one side. Anexample would be a person table and citizenship table relationship. The Paradox issimilar to the Physical Cardinality. A person must have a citizenship and citizenshipmust have a person. But in this case, a person may have multiple citizenships.


2/5

The Association Cardinaltiy is a M:M (many to many) relationship which may be

optional on both sides. An example would be a person table and employer table

relationship where a person may work for several employers or no employer at all.

On the other hand, an employer may have no employee too but can have a several

employees as well. A database implementation for this is to create a third associateentity.

Definition: In set theory, cardinality refers to the number of members in the set. When specifically applied to databasetheory, the cardinality of a table refers to the number of rows (or tuples) contained in a table.

Cardinality Notations

Cardinality specifies how many instances of an entity relate to one instance of another entity.

Ordinality is also closely linked to cardinality. While cardinality specifies the occurances of a relationship,

ordinality describes the relationship as either mandatory or optional. In other words, cardinality specifies the

maximum number of relationships and ordinality specifies the absolute minimum number of relationships.When the minimum number is zero, the relationship is usually called optional and when the minimum

number is one or more, the relationship is usually called mandatory.

There are many notation styles that express cardinality and they are all supported by SmartDraw.

Information Engineering

Chen


3/5

Bachman

Martin


4/5

n the implementation of a structure query language (SQL), the term data cardinalityis used to mean the uniqueness of the data values which are contained in aparticular column, known as attribute, of a database table.

There are actually three types of data cardinality each dealing with columnar valuesets. These types are high-cardinality, normal-cardinality, and low-cardinality.

High data cardinality refers to the instance where the values of a data column are veryuncommon. For example, a data column referring to values for social security numbers shouldalways be unique for each person. This is an example of very high cardinality. Same goes withemail address and user names. Automatically generated numbers are of very high data

cardinality. For instance, in a data table column, a column named USER-ID would containvalues starting with an automatically increments every time a new user is added.

Normal data cardinality refers to the instance where values of a data columnare somewhat uncommon but never unique. For example, a CLIENT table having adata column containing LAST_NAME values can be said to be of normal datacardinality as there may be several entries of the same last name like Jones and mayother varied names in one column. At close inspection of the LAST_NAME column,one can see that there could be clumps of last names side by side with unique lastnames.

Low data cardinality refers to the instance where values of a data column arenot very unusual. Some table columns take very limited values. For instance,Boolean values can only take 0 or 1, yes or no, true or false. Another table columnswith low cardinality are status flags. Yet another example of low data cardinality isthe gender attribute which can take only two values male or female.


5/5

Determining data cardinality is a substantial aspect used in data modeling. This isused to determine the relationships

Several types of cardinality defining relationships between occurrences of entities ontwo sides of the line of relationships exist.

The Link Cardinality is a 0:0 relationship and defined as one side does not need theother to exists

The Sub-type Cardinality is a 1:0 relationship and defined as having one optionalside only.

The Physical Segment Cardinality is 1:1 relationship and it is demonstrated thatboth sides of the relationship are mandatory.

The Possession Cardinality is a 0:M relation (zero to many) relationship on bothsides.

The Child Cardinality is a 1:M mandatory relationship and is one of the mostcommon relationships used most databases

The Characteristic Cardinality is a 0:M relationship which is mandatory on bothsides.

The Paradox Cardinality is 1:M relationship which is mandatory to one side. Anexample would be a person table and citizenship table relationship.

ciation Cardinaltiy is a M:M (many to many) relationship which may be optional on both sides.

A data table's cardinality with respect to another data table is one of the most criticalaspects in database design. For instance, a database hospital may have separatedata tables used to keep track patients and doctors so a many to one relationshipshould be considered by the database designer. If the data cardinality andrelationships are not designed well, the performance of a database will greatly suffer.

discreat presentation data

Documents