Er diagram for customer depositor and account relationship

Draw The Er Diagram For Customer Depositor And Account Relationship

er diagram for customer depositor and account relationship

Relationship Sets. Relationship: is an association among several entities. Example: Hayes depositor A customer entity relationship set account entity. Draw The Er Diagram For Customer Depositor And Account Relationship. Open My ConceptDraw Account and Download ConceptDraw Software Free. The E-R entity-relationship data model views the real world as a set of basic objects entities and For example, consider the two entity sets customer and account. Fig. . Figure E-R diagram with a ternary relationship.

Each car has associated with it zero to any number of recorded accidents.

er diagram for customer depositor and account relationship

From the 6th edition… Construct an ER diagram for a car insurance company whose customers own one or more cars each. Each insurance policy covers one or more cars, and has one or more premium payments associated with it. Each payment is for a particular period of time, and has an associated due date, and the date when the payment was received. Such an entity set is referred to as a strong entity set.

Such an entity set is referred to as a weak entity set. A weak entity set is typically associated with an identifying entity set which is usually strong via a total, one-to-many relationship.

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In such a case, the weak entity typically has a subset of attributes, called a discriminator or partial keythat distinguishes among all entities of the weak entity set associated with one identifying entity. A primary key for the weak entity set can be constructed with two parts: Recall the loan and payment entity sets: The relationship between the weak and strong entity set is specified with a double-diamond.

The discriminator is underlined with a dashed line. Primary key for payment is loan-number, payment-number loan ID amount payment number date loan-payment 37 Weak Entity Sets Cont. The primary key of the strong entity set is not explicitly specified in the weak entity set, since it is implicit in the identifying relationship.

If loan-number were explicitly specified: Payment would be a strong entity set The relationship between payment and loan might not be as clear loan ID amount payment number date loan-payment branch payment-location ID name assets 38 More Weak Entity Set Examples In a university, a course is a strong entity and a section can be modeled as a weak entity.

The discriminator of section would be sec-id, semester and year. If section were modeled as a strong entity then it would have id as an attribute; the relationship with course would be implicit in the id attribute.

Have attributes that do not apply to the higher-level entity set. Participate in relationships that do not apply to the higher-level entity set, e. Lower-level entity sets are said to inherit all the attributes and relationships from the higher-level entity sets to which they are linked.

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Generalization Top-down design process; we designate sub-groupings within an entity set that are distinctive from other entities in the set. The terms specialization and generalization are used interchangeably, for the obvious reasons.

Multiple specializations of an entity set are possible: Possible enterprises to model: Each table has a number of columns, which generally corresponding to the attributes in the corresponding entity or relationship set. The resulting tables can be modified in a variety of ways to support performance, space, or other requirements. A multi-valued attribute M of entity E is represented by a new table with the following attributes: The primary key of E An attribute corresponding to multi-valued attribute M Example: A many-to-one relationship set can be represented just like a many-to-many relationship.

  • Entity-Relationship Modelling
  • bank,branch,customer,loan,account ( Entity Relationship Diagram)

Technically this is not necessary, and in some cases it does not result in a good design. The preceding could be converted to 3 tables directly, or as follows: In this case, 3 tables are probably better why?

For one-to-one relationship sets, the extra attribute can be added to either of the tables corresponding to the two entity sets. Other relationship attributes would be treated similarly. Note that either of the above could introduce null values if the relationship is not total. Returning to the E-R diagram of Figure 2.

er diagram for customer depositor and account relationship

If the relationship set borrower were one-to-many, from customer to loan, then the line from borrower to customer would be directed, with an arrow pointing to the customer entity set Figure 2. Similarly, if the relationship set borrower were many-to-one from customer to loan, then the line from borrower to loan would have an arrow pointing to the loan entity set Figure 2.

Finally, if the relation- ship set borrower were one-to-one, then both lines from borrower would have arrows: If a relationship set has also some attributes associated with it, then we link these attributes to that relationship set. For example, in Figure 2. Also, a compos- ite attribute address, whose component attributes are street, city, state, and zip-code re- places the attributes customer-street and customer-city of customer.

er diagram for customer depositor and account relationship

The attribute street is itself a composite attribute whose component attributes are street-number, street-name, and apartment number. We indicate roles in E-R diagrams by labeling the lines that connect diamonds to rectangles.

er diagram for customer depositor and account relationship

We can specify some types of many-to-one relationships in the case of nonbinary relationship sets. Suppose an employee can have at most one job in each branch for example, Jones cannot be a manager and an auditor at the same branch.

We permit at most one arrow out of a relationship set, since an E-R diagram with two or more arrows out of a nonbinary relationship set can be interpreted in two ways.

Draw The Er Diagram For Customer Depositor And Account Relationship

Suppose there is a relationship set R between entity sets A1, A2, Then, the two possible interpretations are: A particular combination of entities from A1, A2, Thus, the primary key for the relationship R can be constructed by the union of the primary keys of A1, A2, Each of these interpretations has been used in different books and systems. To avoid confusion, we permit only one arrow out of a relationship set, in which case the two interpretations are equivalent.

In Chapter 7 Section 7.