SQL Syntax

Chapter 2 of 40 · Estimated read time: 5 min

The Structure of an SQL Statement

SQL statements are made up of clauses. Each clause starts with a keyword. A SELECT statement follows this order:

SQL Keywords Are NOT Case-Sensitive

All three of these queries do the same thing:

-- All three are identical to the database engine:
SELECT product_name FROM products WHERE price > 500;
select product_name from products where price > 500;
Select Product_Name From Products Where Price > 500;

Semicolons

A semicolon ; marks the end of an SQL statement. It is required when running multiple statements together, and recommended as a habit even for single statements.

-- Running two statements together requires semicolons
SELECT COUNT(*) FROM products;
SELECT COUNT(*) FROM customers;

Whitespace and Line Breaks

SQL ignores extra whitespace and line breaks. These two are identical:

-- Compact (hard to read):
SELECT product_name,price FROM products WHERE category='Electronics' ORDER BY price DESC;

-- Readable (recommended):
SELECT product_name, price
FROM   products
WHERE  category = 'Electronics'
ORDER  BY price DESC;

Comments in SQL

-- This is a single-line comment (standard SQL, works everywhere)

# This is also a single-line comment (MySQL only)

/*
  This is a
  multi-line comment
*/

SELECT product_name  -- inline comment after a clause
FROM products;

Text Values Need Quotes

String (text) values in conditions must be wrapped in single quotes. Numbers do not need quotes.

-- ✅ Correct
SELECT * FROM customers WHERE city = 'Noida';
SELECT * FROM products  WHERE price > 500;

-- ❌ Wrong — missing quotes around text
SELECT * FROM customers WHERE city = Noida;

-- ❌ Wrong — quotes around a number (works in some DBs but is bad practice)
SELECT * FROM products WHERE price > '500';