Example Codes:

1. SQL (Structured Query Language):

   • This is the foundation for all three. It's a standardized language used to communicate with relational databases.
   • SQL statements let you perform tasks like:
     • Retrieving data (SELECT)
     • Inserting new data (INSERT)
     • Updating existing data (UPDATE)
     • Deleting data (DELETE)
     • Defining and manipulating the database structure (CREATE, DROP, ALTER)
   • Imagine SQL as a universal translator you can use with various database vendors.

2. PL-SQL (Procedural Language/SQL):

   • This is an extension of SQL specifically designed for Oracle databases.
   • PL-SQL adds programming capabilities on top of standard SQL. It allows you to:
     • Write procedures and functions to perform complex tasks or reuse code snippets.
     • Implement control flow structures (if/else, loops) for decision-making and repetitive operations.
     • Handle errors and exceptions.
   • Think of PL-SQL as adding a programming layer to SQL for Oracle, making it more powerful for complex database interactions.

3. T-SQL (Transact-SQL):

   • Similar to PL-SQL, T-SQL is a Microsoft-specific extension for Transact-SQL used with Microsoft SQL Server.
   • It offers functionalities similar to PL-SQL, allowing you to:
     • Create stored procedures and functions.
     • Implement control flow.
     • Enhance error handling.
   • T-SQL acts as an extension for SQL Server, providing a programming environment within the database platform.

Here's a table summarizing the key points:

Example Codes:

SQL (Standard for all databases):

This code retrieves all customer names from a table named "Customers":

SELECT CustomerName FROM Customers;

PL-SQL (Oracle Specific):

This code defines a procedure in Oracle that calculates a customer's discount based on their total purchase amount:

CREATE OR REPLACE PROCEDURE CalculateDiscount (customerID IN NUMBER, purchaseAmount IN NUMBER, OUT discountAmount OUT NUMBER) AS
BEGIN
  IF purchaseAmount > 100 THEN
    discountAmount := purchaseAmount * 0.1;  -- 10% discount
  ELSE
    discountAmount := 0;
  END IF;
END;
/

T-SQL (Microsoft SQL Server Specific):

This code defines a function in SQL Server that checks if a specific email address already exists in a table named "Users":

CREATE FUNCTION CheckEmailExists (@email VARCHAR(50))
RETURNS INT
AS
BEGIN
  DECLARE @count INT;
  SELECT @count = COUNT(*) FROM Users WHERE Email = @email;
  RETURN @count;
END;

1. Object-Relational Mapping (ORM):

   • ORMs are libraries that simplify interacting with databases from within a programming language like Python, Java, or C#.
   • They provide a layer of abstraction, allowing you to write code using objects that map to database tables and perform operations without writing raw SQL statements.

2. NoSQL Databases:

   • If your data doesn't fit neatly into a relational structure, NoSQL databases might be a better choice.
   • These databases offer greater flexibility for handling unstructured or schemaless data. Popular options include MongoDB, Cassandra, and Couchbase.

3. Database Management Tools:

   • Many database vendors offer graphical user interfaces (GUIs) or web-based tools for managing databases.
   • These tools allow you to perform tasks like creating tables, editing data, and running queries without writing code.

Here's a quick comparison to help you decide: