SQL Clauses and Operators Explained with Examples (Step-by-Step Guide)

SQL Clauses and Operators Explained with Examples

In SQL, clauses define the structure of a query, and operators help filter and compare data. This guide covers the most common clauses and logical operators every SQL beginner must know.

---

What are SQL Clauses?

SQL clauses are components of SQL statements that define actions, filtering, grouping, and sorting.

1. SELECT Clause

SELECT name, age FROM students;

Fetches name and age columns from the students table.

2. FROM Clause

Specifies the table name:

SELECT * FROM employees;

3. WHERE Clause

SELECT * FROM employees WHERE department = 'Sales';

Filters rows based on a condition.

4. ORDER BY Clause

SELECT name, salary FROM employees ORDER BY salary DESC;

Sorts results in descending order of salary.

5. GROUP BY Clause

SELECT department, COUNT(*) FROM employees GROUP BY department;

Groups results and performs aggregate functions.

6. HAVING Clause

SELECT department, COUNT(*) FROM employees GROUP BY department HAVING COUNT(*) > 5;

Filters groups after GROUP BY.

7. LIMIT Clause

SELECT * FROM products LIMIT 10;

Limits results to the top 10 rows.

---

SQL Operators (AND, OR, IN, NOT, LIKE)

1. AND Operator

SELECT * FROM users WHERE age > 18 AND city = 'New York';

2. OR Operator

SELECT * FROM users WHERE city = 'New York' OR city = 'Chicago';

3. NOT Operator

SELECT * FROM products WHERE NOT price < 100;

4. IN Operator

SELECT * FROM orders WHERE status IN ('Pending', 'Shipped');

5. LIKE Operator

SELECT * FROM customers WHERE name LIKE 'A%';

Finds names starting with 'A'.

---

Best Practices

• Always use WHERE to avoid full-table scans.
• Combine AND / OR wisely to avoid logic errors.
• Use LIMIT when previewing large datasets.

Also Read:

• SQL Basics and Data Types
• All SQL Articles on Sabbir93s

---

FAQs: SQL Clauses and Operators

• Q: What is the difference between WHERE and HAVING?
  A: WHERE filters rows before grouping; HAVING filters groups after grouping.
• Q: What does IN operator do?
  A: It checks if a value exists in a set of values.
• Q: Can I use multiple clauses in a single SQL query?
  A: Yes! Example: SELECT ... FROM ... WHERE ... ORDER BY ...

Stay tuned for advanced SQL tutorials in our next posts.