SQL Syntax and Statements
Introduction to SQL Vocabulary

What is SQL Syntax?

SQL, like any language, has rules. These rules—called syntax—govern how commands must be structured to be understood by a database. Think of it like grammar in English. Say it wrong, and the database won’t know what you mean.

Basic SQL Syntax Rules

• SQL keywords are not case-sensitive (but uppercase is preferred for readability).
• Statements end with a ; semicolon.
• Strings must be enclosed in single quotes: 'Delhi'.

1. SELECT Statement

The most fundamental SQL statement. It’s used to fetch data from a table.

SELECT *
FROM students;

roll_no | name          | class | age | city
--------+---------------+-------+-----+---------
1       | Aarav Kapoor  | 10A   | 15  | Delhi
2       | Meera Nair    | 9B    | 14  | Kochi
3       | Rishi Malhotra| 10A   | 15  | Mumbai

2. INSERT Statement

Used to add new records into a table. Let's insert another student:

INSERT INTO students (roll_no, name, class, age, city)
VALUES (4, 'Pooja Reddy', '9C', 14, 'Hyderabad');

3. UPDATE Statement

Use it to modify existing records. Suppose Pooja moved to Bengaluru:

UPDATE students
SET city = 'Bengaluru'
WHERE roll_no = 4;

4. DELETE Statement

To remove records from a table:

DELETE
FROM students
WHERE roll_no = 2;

5. CREATE TABLE Statement

Let’s build a new table called teachers:

CREATE TABLE teachers (
  teacher_id INT PRIMARY KEY,
  name VARCHAR(50),
  subject VARCHAR(30),
  experience INT
);

6. DROP TABLE Statement

This command deletes an entire table. Use with caution!

DROP TABLE teachers;

7. ALTER TABLE Statement

To change a table’s structure – like adding a new column:

ALTER TABLE students ADD percentage FLOAT;

8. WHERE Clause

Filters results based on a condition:

SELECT name, city FROM students WHERE class = '10A';

name            | city
----------------+--------
Aarav Kapoor    | Delhi
Rishi Malhotra  | Mumbai

9. ORDER BY Clause

To sort data by age in descending order:

SELECT name, age FROM students ORDER BY age DESC;

10. DISTINCT Keyword

To find unique values:

SELECT DISTINCT class FROM students;

10A
9C

SQL Statement Flow – A Real-World Analogy

Imagine managing your school database as a daily task list:

• Start your day: CREATE TABLE
• Add students: INSERT
• Update details if someone shifts school: UPDATE
• Remove alumni: DELETE
• Check class list: SELECT