![]() The primary key constraint is imposed on the column data to avoid null values and duplicate values. In a data model, entities (tables) look like square boxes or rectangular boxes, which contain attributes, and these entities, are connected by lines (relationship). Q9) What is the ER (entity relationship) diagram or ERD?ĮR diagram is a visual representation of entities and the relationships between them. The row is also known as a tuple or record is the horizontal alignment of the data. Q7) What is a column (attribute)?Ī column also known as a field is a vertical alignment of the data and contains related information to that column. Each column has a datatype and based on the situation, integrity constraints are enforced on columns. Related Article: Examples of Data Modellingĭata stored in form of rows and columns is called a table. It would be good if the physical data modeler knows about replication, clustering, and so on. When a data modeler works with the client, his title may be a logical data modeler or a physical data modeler, or a combination of both.Ī logical data modeler designs the data model to suit business requirements, creates and maintains the lookup data, compare the versions of the data model, maintains a changelog, generate reports from the data model and whereas a physical data modeler has to know about the source and target databases properties.Ī physical data modeler should know the technical know-how to create data models from existing databases and tune the data models with referential integrity, alternate keys, indexes, and how to match indexes to SQL code. Q5) What is the difference between a logical and physical data model? The approach by which physical data models are created is called physical data modeling. The important or main object in a database is a table that consists of rows and columns. Database performance, indexing strategy, and physical storage are important parameters of a physical model. The physical data model includes all required tables, columns, relationships, database properties for the physical implementation of databases. Q4) What are a physical data model and physical data modeling? The approach by which logical data models are created is called logical data modeling. ![]() Logical Data Models contain Entity, Attributes, Super Type, Sub Type, Primary Key, Alternate Key, Inversion Key Entry, Rule, Relationship, Definition, etc. This is the actual implementation and extension of a conceptual data model. Q3) What are a logical data model and logical data modeling?Ī logical data model is the version of a data model that represents the business requirements (entire or part of an organization). Physical Data Model: Table, Column, Primary key Constraint, Unique Constraint or Unique Index, Non-Unique Index, Check Constraint, Default Value, Foreign Key, comment, etc. ![]() Logical Data Model: Entity, Attributes, Super Type, Sub Type, Primary Key, Alternate Key, Inversion Key Entry, Rule, Relationship, Definition, business rule, etc ![]() The approach by which data models are created is called data modeling. Top Data Modeling Interview Questions and Answers Q1) What is data modeling?Ī data model is a conceptual representation of business requirements (logical data model) or database objects (physical) required for a database and is very powerful in expressing and communicating the business requirements and database objects.
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