🔍 WHERE Clause in SQL

Last Updated: 7th January 2026

The WHERE clause is used to filter rows in a query. It ensures that only required records are returned based on a condition.

  • WHERE applies conditions to data
  • It filters rows, not columns
  • It works with comparison and logical operators

Hinglish Tip 🗣: WHERE ka kaam hai — kaunsa data chahiye aur kaunsa nahi, ye decide karna.

🧾 Basic Syntax of WHERE

SELECT column_name
FROM table_name
WHERE condition;
  • condition decides which rows are selected
  • Rows that do not satisfy the condition are excluded

⚖️ Comparison Operators in WHERE

Common operators used with WHERE:

  • = equal to
  • != or <> not equal to
  • > greater than
  • < less than
  • >= greater than or equal to
  • <= less than or equal to
SELECT name
FROM students
WHERE age >= 18;

Logical Operators in WHERE

WHERE can combine multiple conditions.

  • AND → all conditions must be true
  • OR → at least one condition must be true
  • NOT → negates a condition
SELECT *
FROM students
WHERE marks > 70 AND age >= 18;

WHERE with NULL Values

  • IS NULL → checks if a column has a NULL value
  • IS NOT NULL → checks if a column does not have a NULL value
SELECT *
FROM students
WHERE age IS NULL;

SELECT *
FROM students
WHERE age IS NOT NULL;

🧪 WHERE with BETWEEN, IN, LIKE Operators

  • IN and NOT IN operators
    • Let say WHERE marks = 30 OR marks = 50 OR marks = 70
    • Use When There is multiple condition join using OR operator
    • e.g. WHERE marks IN (30, 50, 70)
    • e.g. WHERE marks NOT IN (30, 50, 70)
  • BETWEEN operator
    • Let say WHERE marks >= 60 AND marks <= 80
    • Use When There is a range of condition join using AND operator
    • e.g. WHERE marks BETWEEN 60 AND 80
  • LIKE And NOT LIKE operator
    • It is used to match a pattern in a column
    • %char end with given characters
      • e.g. WHERE name LIKE '%A'
    • char% start with given characters
      • e.g. WHERE name LIKE 'A%'
    • %char% contains given characters
      • e.g. WHERE name LIKE '%A%'
    • _char Two characters long and end with given characters
      • e.g. WHERE name LIKE '_A'

Note: We will cover Regular Expressions (regex) in the next section.

Subqueries in WHERE

Syntax:

SELECT column_name
FROM table_name
WHERE column_name IN (SELECT column_name FROM table_name);

Example:

SELECT name
FROM students
WHERE age > (SELECT age FROM students WHERE name LIKE "A%");
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