How to Filter Data in MariaDB

Galaxy Glossary

How do I filter rows with the WHERE clause in MariaDB?

The WHERE clause filters rows that meet specific conditions in a MariaDB SELECT statement.

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Description

Example H2

Example H3

What does the WHERE clause do in MariaDB?

The WHERE clause narrows a SELECT result set to only rows meeting one or more conditions. MariaDB evaluates the clause after reading the table but before returning data, making queries faster and easier to read.

How do I filter rows by an exact value?

Use column = value to match a single value exactly. String literals need single quotes, while numbers do not.

SELECT * FROM Customers WHERE email = 'alice@example.com';

How can I combine multiple conditions?

Combine expressions with AND and OR. Use parentheses to control evaluation order for complex logic.

SELECT * FROM Orders WHERE customer_id = 15 AND total_amount > 100 OR (order_date >= '2024-01-01' AND total_amount <= 50);

How do I filter using pattern matching?

LIKE supports % (any length) and _ (single-char) wildcards. ILIKE provides case-insensitive matching when running with the appropriate collation.

SELECT name FROM Products WHERE name LIKE '%phone%';

How do I filter numeric or date ranges?

Use BETWEEN … AND for inclusive ranges or comparison operators (<, <=, >, >=) for open ranges.

SELECT * FROM Orders WHERE order_date BETWEEN '2024-04-01' AND '2024-04-30';

How do I limit and offset results?

LIMIT n returns up to n rows; combine with OFFSET to paginate results.

SELECT * FROM Products WHERE stock > 0 ORDER BY name LIMIT 10 OFFSET 20;

What are best practices for filtering data?

Create indexes on columns used in frequent WHERE clauses, avoid functions on indexed columns, and prefer parameterized queries to prevent SQL injection.

Why How to Filter Data in MariaDB is important

How to Filter Data in MariaDB Example Usage


-- Find the last 5 orders over $200 made this month by customer “Alice”
SELECT o.id, o.order_date, o.total_amount
FROM Orders o
JOIN Customers c ON c.id = o.customer_id
WHERE c.name = 'Alice'
  AND o.total_amount > 200
  AND o.order_date >= DATE_FORMAT(CURDATE(), '%Y-%m-01')
ORDER BY o.order_date DESC
LIMIT 5;

How to Filter Data in MariaDB Syntax


SELECT column_list
FROM table_name
WHERE condition1 [AND|OR condition2 ...]
[ORDER BY column [ASC|DESC]]
[LIMIT row_count] [OFFSET row_offset];

Examples with ecommerce tables:
1. Exact match:
   SELECT * FROM Customers WHERE id = 5;
2. Range:
   SELECT * FROM Orders WHERE total_amount BETWEEN 50 AND 200;
3. Pattern:
   SELECT * FROM Products WHERE name LIKE '%Case%';

Common Mistakes

Using functions on indexed columns (e.g., UPPER(email) = ...) forces full table scans. Fix by storing computed values or using case-insensitive collations.
Forgetting parentheses in mixed AND/OR logic changes results. Always group related conditions explicitly to avoid unintended matches.