Data Modeling

☛ 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.

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

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

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

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

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

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

☛ 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.

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.

☛ 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.

☛ 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.

☛ 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.

☛ 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.