I.M (FINALS) | LESSON 3 - 4

Subquery

This is a query inside a query, it is also called an INNER QUERY

Outer Query

This is what you call the main query that includes the subquery

Inline Views

A subquery that is created in the FROM clause is called?

Nested Query

This is a subquery that can be frequently found in the WHERE clause

Entity Relationship Diagram (ERD)

This is a diagram that shows the relationship of all entity created in database and explains its logical structure.

• Rectangles

• Ovals

• Diamonds

What are the three basic symbols ERD uses?

Peter Chen

Who is the creator of Chen’s notation invented in 1976?

Chen’s Notation

This is invented in 1976, a detailed way of notation. This notation is one of the first in designing software and still popular in making ERD.

Entity

This can be a person, place, object, event, or concept stored in database.

Strong Entity

This symbol can exist without the need of any other entity and has primary key.

Weak Entity

This symbol cannot exist without the strong entity and doesn’t have primary key

Associative Entity

This relates the instances of other entity using definite attributes to the relationship among them.

Attributes

This is a property that describes the entity. It is connected to the entity using straight lines.

Relationship

This is used to label the association of entities.

Key Attribute

This uniquely identifies the strong entity.

Partial Key Attribute

This is known as the discriminator, it uniquely identifies the weak entity.

Multivalued Attribute

This is an attribute that can have many value.

Derived Attribute

The value can be computed from other attributes which may or may not be inserted in the database.

Composite Attributes

These are attributes that can be divided into parts.

Relationship

This is used to label the association of entities. It is usually used verbs or verb phrases to identify the relation. This uses the diamond or rhombus symbol.

Mandatory Relationship

Seeing the illustration above, what kind of optionality of relationship is presented?

Optional Relationship

Seeing the illustration above, what kind of optionality of relationship is presented?

Cardinality of Relationship

This defines the degree or number of attributes of the relationship connecting two entities. it is characterized by “1”, “N” or “M” which is located at the end of the relationship.