MySQL WHERE Clause

The WHERE clause filters which rows a query acts on. Without it, a SELECT returns every row, an UPDATE changes every row, and a DELETE removes every row. With WHERE, you narrow the operation down to only the rows that match a specific condition.

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Syntax

SELECT column1, column2
FROM table_name
WHERE condition;

The same WHERE clause works identically with UPDATE and DELETE.

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Sample Table

id	name	city	age
1	Rahim Uddin	Dhaka	22
2	Sara Begum	Chittagong	20
3	Karim Ali	Sylhet	23
4	Nila Akter	Dhaka	21
5	Rafi Hossain	Rajshahi	24

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Comparison Operators

The WHERE clause supports these comparison operators:

Operator	Meaning	Example
=	Equal to	WHERE city = 'Dhaka'
!= or <>	Not equal to	WHERE city != 'Dhaka'
>	Greater than	WHERE age > 21
<	Less than	WHERE age < 23
>=	Greater than or equal	WHERE age >= 22
<=	Less than or equal	WHERE age <= 21

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Text Conditions

String values must be wrapped in single quotes. The comparison is case-insensitive by default in MySQL:

-- Exact match on city
SELECT * FROM students WHERE city = 'Dhaka';

id	name	city	age
1	Rahim Uddin	Dhaka	22
4	Nila Akter	Dhaka	21

-- Rows where city is NOT Dhaka
SELECT * FROM students WHERE city != 'Dhaka';

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Numeric Conditions

Numbers do not need quotes:

-- Students older than 21
SELECT name, age FROM students WHERE age > 21;

name	age
Rahim Uddin	22
Karim Ali	23
Rafi Hossain	24

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Date Conditions

Dates must be wrapped in single quotes and written in YYYY-MM-DD format:

-- Orders placed after a specific date
SELECT * FROM orders WHERE order_date > '2025-01-01';

-- Records from exactly one date
SELECT * FROM orders WHERE order_date = '2025-06-15';

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WHERE with UPDATE and DELETE

The WHERE clause works identically in UPDATE and DELETE:

-- Update only Karim Ali's row
UPDATE students SET city = 'Barishal' WHERE id = 3;

-- Delete only students under 21
DELETE FROM students WHERE age < 21;

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Key Points to Remember

• WHERE filters rows before the query acts on them — only matching rows are returned, updated, or deleted.
• String values require single quotes; numbers and booleans do not.
• Date values require single quotes in YYYY-MM-DD format.
• String comparisons are case-insensitive by default in MySQL.
• Both != and <> mean "not equal to" — they are interchangeable.
• WHERE works the same way in SELECT, UPDATE, and DELETE.