SQL Tutorial - Full Database Course for Beginners

Introduction to SQL

• SQL: Language used to interact with relational database management systems (RDBMS).
• RDBMS: Software to create and manage databases. Examples include MySQL, Oracle, PostgreSQL, MariaDB.
• This course covers the basics of databases, SQL, and different types of databases, advancing to database schema design.
• Giraffe Academy: Course resources and additional information can be found on GiraffeAcademy.com.

What is a Database?

• Database (DB): A collection of related information.
• Examples: Phonebook, shopping list, Facebook's user base.
• Storage methods: Paper, mind, computer (digital).
• Purpose: Organize and retrieve large amounts of information efficiently.

Types of Databases

1. Relational Databases (SQL) [Structured Query Language]
   • Data organized into tables (with rows and columns).
   • Common RDBMS: MySQL, Oracle, PostgreSQL, MariaDB.
   • Use SQL for CRUD operations.
2. Non-Relational Databases (NoSQL)
   • Various models: Document (JSON, XML), Graph, Key-Value stores.
   • No standard query language; specific to implementation (e.g., MongoDB, Firebase).

Basics of SQL

• CRUD Operations: Create, Read, Update, Delete.
• Queries: Instructions to RDBMS for specific information (e.g., Google search). Use SQL for query writing.
• SQL Code: Standardized language across RDBMS with slight variations.

Installing MySQL and PopSQL

1. MySQL Installation
   • Download MySQL Community Server.
   • Installation steps.
   • Configure the MySQL server, and set up a root password.
2. PopSQL Installation
   • Download and install PopSQL for query writing.
   • Connect PopSQL with MySQL server locally.
   • Create a database (e.g., giraffe).

SQL Basics

Tables and Keys

• Table Structure: Columns and rows. Each table requires a primary key to uniquely identify each row.
  • Primary Key (PK): Unique identifier (e.g., student_id).
  • Foreign Key (FK): Attribute linking to primary key in another table.
  • Composite Key: Composition of multiple columns as PK.
• Defining Relationships: Use FK to link tables.

Creating, Altering, and Dropping Tables

• Creating a Table: CREATE TABLE SQL command defines column types (e.g., INT, VARCHAR).
• Altering a Table: ALTER TABLE to add or drop columns.
• Dropping a Table: DROP TABLE command.

Inserting, Updating, and Deleting Records

• Insert Data: INSERT INTO command, specifying column values.
• Updating Data: UPDATE ... SET ... WHERE .... Change existing records.
• Delete Data: DELETE FROM ... WHERE .... Remove records.

Querying Data

• SELECT Statement: Retrieve data from tables.
• Filtering: WHERE clause to filter specific records.
• Sorting: ORDER BY clause to sort records.
• Limiting Results: LIMIT clause to limit the number of results.
• Joins: Combine rows from multiple tables based on related columns (INNER JOIN, LEFT JOIN, RIGHT JOIN).

Aggregation and Grouping

• Functions: COUNT(), SUM(), AVG(), etc., for aggregate calculations.
• Grouping: GROUP BY to aggregate results into groups.
• Using HAVING: Filter groups per condition.

Advanced SQL Concepts

• Subqueries: Nested queries within a SELECT, INSERT, UPDATE, or DELETE statement.
• Unions: Combine results from multiple SELECT statements (UNION, UNION ALL to include duplicates).
• Triggers: Automated actions performed in response to certain events (BEFORE INSERT, AFTER INSERT etc.).

Database Design and ER Diagrams

• ER Diagram: Conceptual map showing entities and relationships.
  • Entities: Objects or concepts (e.g., Student, Class). Represented by rectangles.
  • Attributes: Properties of entities (e.g., name, GPA). Represented by ovals.
  • Relationships: Connections between entities (e.g., Takes). Represented by diamonds.
  • Cardinality: Denotes relationships' nature (e.g., 1:1, 1:N, N:M).

ER Diagram to Database Schema

• Mapping Entities: Create necessary tables in the database.
• Mapping Relationships: Define relationships using FK and constraints.
• Handling Weak Entities: Use identifying relationships and partial keys.
• Converting to Schema: From ER diagram to create tables, define PKs, FKs, and map relationships.

Summary

• Purpose: Organize and manipulate data using SQL in RDBMS.
• Techniques: Creating, altering tables, CRUD operations, querying, and advanced SQL functions.
• Design: Use ER diagrams to design a systematic and relational database schema.

Final Thoughts

• Practice: Essential to master SQL techniques and database design principles.

Continue exploring detailed concepts and practice exercises on GiraffeAcademy.com