Pl/Sql Interview Questions for Experienced Pdf - 1

Question: 1

What are the components of logical data model?

Following are the components of the logical data model:

• Entity – Refers to an object of interest, that is, something that we want to store information about. In a relational database structure, each entity has its own table, that is, a structure of rows and columns.
• Attribute – Refers to the property or the information of the entity that we are interested in. It is stored as a column of the table and has specific data type associated with it.
• Record – Refers to a collection of all the properties associated with an entity for one specific condition. it is represented by a row in a table.
• Tuple – Refers to the design of a record.
• Domain – Refers to the description of the legitimate values for an attribute. It is the set of all the possible values for that attribute.
• Relation – Represents a relation between two entities. Therefore, a relation database is a collection of entities and relationships.
• Relational database – Refers to a set of related entities, which is used to store required information as per the design.

Question: 2

What is transitive dependency?

A transitive dependency is the situation when an attribute indirectly depends on another attribute through a third attribute.

Question: 3

What is multi valued dependency?

A multi valued dependency is the situation when an attribute is dependent on another attribute.

However, there are multiple rows in a table representing the dependency. This situation can happen when there is at least one or more attribute which is dependent on A and it requires to have multiple rows of A and B to represent all the possible combinations.

A multi valued dependency is represented by A >> B.

Question: 4

Which sorting algorithm does oracle follow?

Oracle used to follow a balanced binary tree sorting algorithm to effectively build an in memory index on the incoming data.

Binary tree search places a huge memory and CPU overhead on the system for large searches; therefore, Oracle introduced an algorithm based on heap sort, which is more efficient.

However, it also has a limitation of re ordering incoming rows even when the data is not arriving out of order.