Data Modeling and Normalization Concepts

Data Modeling

• Definition: Process of creating a data model to visually represent data structures and relationships.
• Types of Data Models:
  • Conceptual Model: High-level view, outlines data entities and relationships.
  • Logical Model: More detailed, defines data elements and their relationships without focusing on physical implementation.
  • Physical Model: Describes how data is stored in the database, including tables, columns, data types, etc.
• Key Components:
  • Entities: Objects or things in the database (e.g., customers, orders).
  • Attributes: Characteristics of entities (e.g., customer name, order date).
  • Relationships: Connections between entities (e.g., one-to-many, many-to-many).

Database Normalization

• Definition: Process of organizing data to reduce redundancy and improve data integrity.
• Normal Forms:
  • First Normal Form (1NF): Eliminate repeating groups; each column must contain atomic values.
  • Second Normal Form (2NF): Meet 1NF and eliminate partial dependencies; all non-key attributes must depend on the entire primary key.
  • Third Normal Form (3NF): Meet 2NF and remove transitive dependencies; non-key attributes must depend only on the primary key.
  • Boyce-Codd Normal Form (BCNF): A stronger version of 3NF; every determinant must be a candidate key.
• Benefits:
  • Reduces data redundancy.
  • Enhances data integrity and consistency.
  • Simplifies database maintenance.

SQL Queries

• Definition: Structured Query Language (SQL) used to interact with databases for querying, updating, and managing data.
• Basic SQL Commands:
  • SELECT: Retrieve data from one or more tables.
    • Syntax: SELECT column1, column2 FROM table WHERE condition;
  • INSERT: Add new rows to a table.
    • Syntax: INSERT INTO table (column1, column2) VALUES (value1, value2);
  • UPDATE: Modify existing rows in a table.
    • Syntax: UPDATE table SET column1 = value1 WHERE condition;
  • DELETE: Remove rows from a table.
    • Syntax: DELETE FROM table WHERE condition;
• Joins:
  • INNER JOIN: Returns records with matching values in both tables.
  • LEFT JOIN: Returns all records from the left table and matched records from the right table.
  • RIGHT JOIN: Returns all records from the right table and matched records from the left table.
  • FULL OUTER JOIN: Returns records when there is a match in either table.
• Aggregate Functions:
  • COUNT(): Returns the number of rows.
  • SUM(): Returns the total sum of a numeric column.
  • AVG(): Returns the average value of a numeric column.
  • MAX()/MIN(): Returns the highest/lowest value in a column.

Data Modeling

• Data Modeling: Visual representation of data structures and relationships to facilitate understanding and management.
• Types of Data Models:
  • Conceptual Model: High-level overview of data entities and their interrelations, suitable for preliminary design.
  • Logical Model: Detailed depiction focusing on data elements and relationships without considering physical storage.
  • Physical Model: Specifies data storage structures such as tables, columns, data types, and indexes.
• Key Components:
  • Entities: Fundamental objects in the database (e.g., customers, products).
  • Attributes: Specific properties of the entities (e.g., customer name, product price).
  • Relationships: Links between entities, such as one-to-many (e.g., a customer and multiple orders) or many-to-many (e.g., students and courses).

Database Normalization

• Normalization: Technique for organizing database structure to minimize redundancy and enhance integrity.
• Normal Forms:
  • First Normal Form (1NF): Ensures that each column contains only atomic (indivisible) values; eliminates repeating groups.
  • Second Normal Form (2NF): Builds on 1NF by removing partial dependencies; all non-key attributes must relate to the entire primary key.
  • Third Normal Form (3NF): Expands 2NF by eliminating transitive dependencies; non-key attributes must depend solely on the primary key.
  • Boyce-Codd Normal Form (BCNF): Enhanced version of 3NF ensuring every determinant is a candidate key.
• Benefits of Normalization:
  • Reduces duplication of data across the database.
  • Improves consistency and integrity of data.
  • Simplifies processes for database maintenance and updates.

SQL Queries

• Structured Query Language (SQL): Standard language for managing and manipulating relational databases.
• Basic SQL Commands:
  • SELECT: Command for retrieving specific data from tables. Syntax example: SELECT column1, column2 FROM table WHERE condition;
  • INSERT: Adds new records to a designated table. Syntax example: INSERT INTO table (column1, column2) VALUES (value1, value2);
  • UPDATE: Modifies existing data entries in a table. Syntax example: UPDATE table SET column1 = value1 WHERE condition;
  • DELETE: Removes specified records from a table. Syntax example: DELETE FROM table WHERE condition;
• Joins:
  • INNER JOIN: Yields records with matches in both tables.
  • LEFT JOIN: Retrieves all records from the left table and matched records from the right.
  • RIGHT JOIN: Collects all records from the right table alongside matched records from the left.
  • FULL OUTER JOIN: Gathers records with matches in either table.
• Aggregate Functions:
  • COUNT(): Computes the total number of rows in a query result.
  • SUM(): Calculates the total of a numerical column.
  • AVG(): Averages the numeric values in a specified column.
  • MAX()/MIN(): Determines the maximum or minimum values within a column.