Data Modeling Interview Preparation Guide

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☛ Reverse Engineering is a process useful for creating the data modes from database and scripts.
☛ In this tools have options to connect the database by which we can reverse engineer a database into a data model.

☛ There are three basic elements
☛ Entities which we seek information
☛ Attributes the data collect about the entities.
☛ Relationship provide the structure needed to draw information from multiple entities.

☛ Data stored in a form of rows and column is called as table.
☛ Each column has data type and based on the situation, integrity constraints are enforced on columns.

☛ Foreign key constraint is a column, that is used to establish and enforce a link between the data in two tables.
☛ It is defined as constraint create or modify a table.

In a database, high cardinality means more unique values are stored in a column and vice versa.One to One, One to many, and many to many are different types of cardinalities.

☛ A Data modelling repository is storage area, where metadata of a data model is stored.
☛ The data is stored in different from the software perspective, organization’s perspective and usage perspective.
☛ Repository can be stored any, where either in a data base or locally within any system.

☛ Constraint is a rule imposed on data.
☛ Different types of constraint:
☛ Primary key
☛ Unique
☛ Not null
☛ Foreign key
☛ Composite foreign key
☛ Check constraint

In relational databases, a foreign key is a field in one table which is used to uniquely identify a row of another table.

Standalone column is a table will be connected to the primary key of the same table. It is called recursive relationship.

Unique constraint is imposed on the column data to avoid duplicate values, but it will contain NULL values.

Visual representation of objects in a relational database is called as relational data modelling, table contains row and copy.

Index is imposed on column or set of columns for fastest retrieval of data.

The primary key constraint is imposed on the column data to avoid null value and duplicate values.

It is known as tuple or record is the horizontal alignment of the data.

Logical Data Model Contain:
Entry, Super Type, Sub Type, primary key, Alternate key, Inversion key Entry, Rule, Relationship, Definition, Business Rule, Entity, etc.

Physical Data Model Contain:
Table, Column, Primary key Constraint, Unique Index, Non Unique Index, Check constraint, Default value, Foreign key, Comment etc.

☛ It is a process by which DDL scripts are generated from the data model.
☛ Data modelling tools have options to create DDL Scripts by connecting with various databases.
☛ With its scripts and database can be created.

It is a database object to generate unique number

☛ De- Normalization is a process of adding redundancy to the data.
☛ It helps us to quickly retrieve the information from the database.

☛ Identifying
☛ Non – Identifying Relationship
☛ Self –Recursive Relationship

Column also known as field is a vertical alignment of a data and constrains related to that columns.

Data model is a conceptual representation of Business Requirement (logic data model) or Data Base objects required for a database and very powerful in expressing and communicating the business requirements and database objects.

A group of columns in a foreign key, it is called as a composite foreign key constraint

☛ OLTP stands for online transactional processing.
☛ Data models are constructed for transactions is called OLTP data modelling.

Sequence is a database object to generate unique number.

Check constraint is used to check range of values in a column.