1️⃣5️⃣ 🔍 MySQL Regular Expressions & Wildcards – Advanced Pattern Matching in SQL

Pattern-based queries are essential for dynamic search features, data validation, and advanced filtering in SQL. MySQL offers two powerful tools for this: wildcards (with LIKE) and regular expressions (REGEXP). This article walks you through their usage, examples, patterns, and performance tips.

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🧲 Introduction – Why Use Regular Expressions & Wildcards?

Searching partial matches, filtering dynamic text, or validating structured data in MySQL requires pattern-matching. You can achieve this using:

✅ LIKE and NOT LIKE with wildcards
🧠 REGEXP and RLIKE with regular expressions

These tools boost SQL’s flexibility and help implement intelligent search and filtering logic.

🎯 In this guide, you’ll learn:

• How to use % and _ wildcards with LIKE
• How to perform regex-based search with REGEXP/RLIKE
• Common pattern examples and real use cases
• Best practices and performance considerations

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📘 Topics Covered

🔹 Topic	📄 Description
🔡 MySQL Wildcards	Use % and _ with LIKE/NOT LIKE
🧮 REGEXP Syntax	Use regex patterns in WHERE clauses
🧬 Common REGEXP Patterns	Handy regex examples for MySQL
🧪 Case Sensitivity	Control sensitivity using BINARY
🧠 Wildcards vs REGEXP	Know when to use which
🚀 Real-World Examples	Practical implementations
📘 Best Practices	Optimization tips
📌 Summary & FAQ	Recap and answers

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🔡 1. MySQL Wildcards – Basic Pattern Matching with LIKE

🔹 % – Match Zero or More Characters

SELECT * FROM users WHERE username LIKE 'a%';

✅ Matches: alice, adam, alex123

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🔹 _ – Match a Single Character

SELECT * FROM products WHERE sku LIKE 'P_23';

✅ Matches: P123, PA23
❌ Not: PP123

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🔹 Combine % and _

SELECT * FROM files WHERE name LIKE '_temp%';

✅ Matches: 1temp, a_tempfile

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🔹 NOT LIKE – Invert the Match

SELECT * FROM orders WHERE order_number NOT LIKE '2023%';

✅ Returns records not starting with 2023

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🧮 2. MySQL REGEXP – Advanced Pattern Matching

MySQL supports POSIX-style regular expressions with:

SELECT * FROM table WHERE column REGEXP 'pattern';

🔹 Synonym: RLIKE

SELECT name FROM users WHERE name RLIKE '^A';

✅ Matches names starting with A

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🧬 3. Common REGEXP Patterns in MySQL

Pattern	Meaning	Example Matches
^abc	Starts with abc	abcde, abcdefxyz
xyz$	Ends with xyz	helloxyz, 123xyz
a.b	a followed by any char, then b	acb, a_b
[aeiou]	Any one vowel	apple, end
[^0-9]	Not a digit	Z, !, a
[A-Z]{3}	3 uppercase letters	ABC, XYZ
[0-9]{3,5}	3–5 digits	123, 45678
`a	b`	Matches a or b

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🔹 Example – Names Ending in ‘son’

SELECT name FROM employees WHERE name REGEXP 'son$';

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🔹 Example – Emails from Gmail

SELECT email FROM users WHERE email REGEXP '@gmail\\.com$';

✅ \\.com escapes the . (dot)

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🧪 4. Case Sensitivity in REGEXP

By default, REGEXP is case-insensitive:

SELECT 'abc' REGEXP 'A'; -- Returns 1

To enable case sensitivity:

SELECT name FROM users WHERE BINARY name REGEXP '^A';

✅ Matches names only starting with uppercase A

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🧠 Wildcards vs REGEXP – When to Use What?

Feature	Use Case	Syntax
LIKE	Simple pattern matching	%, _
REGEXP	Complex validation/alternation	[], {}
RLIKE	Synonym for REGEXP	Interchangeable

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🚀 Real-World Use Cases

Scenario	Pattern Used	Matches
Search SKUs starting with X	LIKE 'X%'	X123, X-ABC
ZIP code validation	REGEXP '^[0-9]{5}$'	12345
Emails ending in .edu	REGEXP '\\.edu$'	user@uni.edu
Names starting with J or K	REGEXP '^[JK]'	John, Kevin

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📘 Best Practices

✅ Tip	💡 Why It Matters
Use LIKE for basic matches	Faster and uses indexes
Escape special characters	Avoids unexpected matches or errors
Don’t use REGEXP on large sets	Slower than indexed LIKE
Index prefix columns	Boosts performance on LIKE 'abc%'
Test REGEXP before production	Ensures it works correctly and efficiently

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📌 Summary – Recap & Next Steps

MySQL wildcards (LIKE) and regular expressions (REGEXP) allow powerful pattern-based querying, from basic prefix searches to advanced character validation. Choose the right method based on query complexity and performance needs.

🔍 Key Takeaways

• % matches many characters; _ matches one
• REGEXP allows advanced validation and custom formats
• Use BINARY for case-sensitive regex
• Prefer LIKE when performance and indexing are important
• Always test regex thoroughly in development

⚙️ Real-World Relevance

These pattern tools are essential for search filters, form validations, reporting filters, email/username checks, and log parsing in real-world applications.

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❓ FAQ – MySQL REGEXP & Wildcards

❓ What’s the difference between % and _ in LIKE?

✅ % matches any number of characters
✅ _ matches exactly one character

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❓ Is REGEXP case-sensitive?

❌ No. Use BINARY before the column to enforce case-sensitivity.

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❓ Can I use REGEXP in a WHERE clause?

✅ Yes. It behaves like other conditional operators (=, LIKE, etc.)

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❓ Is RLIKE different from REGEXP?

❌ No. RLIKE is just a synonym of REGEXP.

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❓ Can I mix LIKE and REGEXP together?

❌ No. They use different syntaxes—choose either for a query.

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