How to Filter Data in MySQL

Galaxy Glossary

How do I filter data in MySQL?

Use the WHERE clause with comparison, logical, or pattern operators to return only rows matching specified conditions.

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Description

Example H2

Example H3

What does filtering data mean in MySQL?

Filtering means using the WHERE clause in SELECT, UPDATE, or DELETE statements to restrict rows returned or affected based on column values.

Which clauses and operators can I use to filter?

WHERE clause

The WHERE clause evaluates each row and returns it only if the condition resolves to TRUE.

Comparison operators (=, <, >, <=, >=, !=)

Use numeric or string comparisons to match exact or range values, for example price > 50.

Logical operators (AND, OR, NOT)

Combine multiple conditions to build complex filters.

Pattern operators (LIKE, REGEXP)

Match substrings or regular expressions for flexible searches.

IN, BETWEEN, IS NULL

Test for membership, ranges, or NULL values concisely.

How do I filter orders above $100?

SELECT id, customer_id, total_amount FROM Orders WHERE total_amount > 100;

How do I chain multiple conditions?

SELECT * FROM Products WHERE stock < 10 AND price <= 20;

Can I filter on joined tables?

Yes.Place the filter after the JOIN or in an ON clause to define row matching.

Example

SELECT o.id, c.name, o.total_amount FROM Orders o JOIN Customers c ON c.id = o.customer_id WHERE o.order_date >= '2024-01-01';

Best practices for filtering

Index frequently filtered columns, avoid functions on indexed columns, use prepared statements to prevent SQL injection, and prefer = or IN over LIKE when possible.

Why How to Filter Data in MySQL is important

How to Filter Data in MySQL Example Usage


SELECT p.id, p.name, p.price
FROM Products p
JOIN OrderItems oi ON oi.product_id = p.id
JOIN Orders o ON o.id = oi.order_id
WHERE o.order_date BETWEEN '2024-01-01' AND '2024-06-30'
  AND p.stock > 0
ORDER BY p.price DESC;

How to Filter Data in MySQL Syntax


SELECT select_list
FROM table_name
[JOIN ...]
WHERE condition
[GROUP BY ...]
[HAVING ...]
[ORDER BY ...]
[LIMIT ...];

-- Examples
-- 1. Exact match
SELECT name, email
FROM Customers
WHERE email = 'alice@example.com';

-- 2. Range filter
SELECT *
FROM Orders
WHERE total_amount BETWEEN 50 AND 200;

-- 3. Multiple conditions
SELECT *
FROM Products
WHERE price < 20 AND stock > 0;

-- 4. IN list
SELECT *
FROM Orders
WHERE id IN (101,102,103);

-- 5. Join filter
SELECT o.id, c.name, o.total_amount
FROM Orders o
JOIN Customers c ON c.id = o.customer_id
WHERE o.order_date >= '2024-01-01';

Common Mistakes

Mixing AND and OR without parentheses changes logic. Always wrap OR groups: WHERE status = 'shipped' AND (total_amount > 100 OR customer_id = 5).
Using LIKE '%value%' on large unindexed columns causes full-table scans. Create an index on the column or switch to full-text search for better performance.

Frequently Asked Questions (FAQs)

Does filtering slow down queries?

Filtering can be fast when the filtered columns are indexed. Without indexes, MySQL must scan the entire table, increasing response time.

How do I filter case-insensitively?

MySQL string comparisons are case-insensitive when the column collation ends with _ci. For explicit control, use LOWER() and compare against lowercase literals.