Learning of SQL Day 2

Day 2: Basic SQL Syntax

Introduction:

• Understanding the basic syntax of SQL is essential for writing queries to manage and retrieve data.

Key Concepts:

• SQL Statements: Instructions to perform tasks.

• Clauses: Components of SQL statements (e.g., SELECT, WHERE).

• Keywords: Reserved words in SQL (e.g., SELECT, INSERT).

• Identifiers: Names given to database objects like tables, columns.

• Expressions: Combinations of values, operators, and SQL functions.

Basic SQL Commands:

1. SELECT Statement:

   • Used to retrieve data from a database.

SQL

-- Select all columns from the Students table
SELECT * FROM Students;

-- Select specific columns from the Students table
SELECT FirstName, Age FROM Students;

2. INSERT Statement:

   • Used to insert data into a table.

sql

-- Insert a single row of data into the Students table
INSERT INTO Students (StudentID, FirstName, LastName, Age)
VALUES (2, 'Jane', 'Smith', 22);

3. UPDATE Statement:

   • Used to modify existing data in a table.

sql

-- Update the Age of the student with StudentID = 2
UPDATE Students
SET Age = 23
WHERE StudentID = 2;

4. DELETE Statement:

   • Used to delete data from a table.

sql

-- Delete the student with StudentID = 1
DELETE FROM Students
WHERE StudentID = 1;

Practice Exercise:

• Create a table named Courses with columns CourseID, CourseName, and Credits.

• Insert three courses into the Courses table.

• Write a query to select all courses.

• Update the Credits for one of the courses.

• Delete one course.