☛ 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.
Standalone column is a table will be connected to the primary key of the same table. It is called recursive relationship.
☛ Constraint is a rule imposed on data.
☛ Different types of constraint:
☛ Primary key
☛ 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.
Unique constraint is imposed on the column data to avoid duplicate values, but it will contain NULL values.