How to Retrieve Information Using SQL

Entity-Relationship (E-R) Model 

E-R refers to a design of a data collection that can be structured to a database. It uses a diagram to describe the structure of a database by showing the connection between entity sets. The significant aspects of the model are relationship set and entity set. For instance, a student roll number can distinctively identify a student from a set of students.

Database Normalization 

It refers to a method of organizing tables in a way that minimizes dependency and redundancy of data. (Jukic, 2014) The technique portions huge tables into smaller tables and uses their relationships to link them. The objective of database normalization is to ensure data is stored in an organized manner and get rid of non-essential data. For instance, in the table below, the worker named Khan is found in two departments, therefore if you need to update the department of the worker who appears twice, then you need to update the department for all the workers.

Primary Key 

It refers to a field with a column or an existing table column created by the database based on the established order. (Reese, 2015) It's planned to parse data in the database and establish how different tables are related. The primary key must contain a unique value and has no null values. For instance, a client conducting a bank query may be asked to provide a surname. A familiar name may return several results, but using first essential warrants a single result.

Foreign Keys 

It refers to a set of a column or a column in a rational data-collection table that lays out a connection between information in two tables. (Pirk, 2011) For example, a relationship between client and order tables can be created by establishing a foreign key into the order table that is called CLIENT_ID in the client table. The column will exist in both order and client tables.

Relational Database 

This refers to the assembling of data with the existing connection between them for easy retrieval. The information is stored in rows and columns in tables. For example, a business database would contain a table format with the client's name, phone number, and address while another will describe the order.

References 

Jukic, N. V. (2014). Database systems: Introduction to databases and data warehouses. Pearson , 200.

Pirk, H. M. (2011). Accelerating Foreign-Key Joins using Asymmetric Memory Channels. Ipp. 27-35). ADMS@ VLDB , 27-35.

Reese, G. (2015). Database Programming with JDBC and JAVA. . " O'Reilly Media, Inc.".