🔍 MySQL REGEXP, RLIKE, and NOT REGEXP – Advanced Pattern Matching Explained

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🧲 Introduction – What Is REGEXP in MySQL?

MySQL’s REGEXP operator allows for regular expression-based pattern matching, providing far more flexibility than LIKE. It’s used for:

• 🔎 Validating text formats
• 🧠 Advanced searching (e.g., ranges, character classes)
• ❌ Filtering text that does not match a pattern using NOT REGEXP

🎯 In this guide, you’ll learn:

• How to use REGEXP, RLIKE, and NOT REGEXP
• Syntax and supported regular expression features
• Real-world examples
• Tips and performance notes

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📌 1. REGEXP – Match Using Regular Expressions

🔹 Syntax

SELECT * FROM table_name WHERE column REGEXP 'pattern';

✅ Returns rows where column matches the regex pattern.

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🔹 Example – Names Starting with A or B

SELECT name FROM employees WHERE name REGEXP '^[AB]';

✅ Matches: Alice, Ben
❌ Skips: Charlie, David

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🔁 2. RLIKE – Synonym for REGEXP

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

✅ Equivalent to REGEXP 'son$'
🔄 Use either—they behave exactly the same.

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🚫 3. NOT REGEXP – Invert Match Logic

SELECT name FROM customers WHERE email NOT REGEXP '@gmail\\.com$';

✅ Returns customers whose emails do not end with @gmail.com.

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🧠 4. Common REGEXP Patterns in MySQL

Pattern	Description	Example Match
^abc	Starts with abc	abcdef, abc123
xyz$	Ends with xyz	abcxyz, 123xyz
a.b	a followed by any one character, then b	acb, a_b
[aeiou]	Any vowel	apple, echo
[^0-9]	Not a digit	abc, Z
[A-Z]{2,4}	2–4 uppercase letters	AB, XYZ, TEST
`foo	bar`	Match foo or bar
[0-9]{5}	Exactly 5 digits	12345, 67890

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🔹 Escaping Special Characters

Use \\ to escape regex meta characters:

SELECT email FROM users WHERE email REGEXP '\\.edu$';

✅ Matches emails ending with .edu

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🔍 5. Case Sensitivity in REGEXP

• REGEXP is case-insensitive by default in MySQL:

SELECT 'apple' REGEXP 'A'; -- Returns 1 (match)

• Use BINARY for case-sensitive regex:

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

✅ Matches only names starting with uppercase A

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🔄 6. REGEXP Use Cases

Use Case	Pattern/Usage
Validate US ZIP code	REGEXP '^[0-9]{5}$'
Match phone numbers with hyphens	REGEXP '^[0-9]{3}-[0-9]{3}-[0-9]{4}$'
Filter invalid usernames	NOT REGEXP '^[a-zA-Z0-9_]+$'
Check for special characters	REGEXP '[^a-zA-Z0-9]'
Find names ending in “son”	REGEXP 'son$'

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📘 REGEXP vs LIKE – Key Differences

Feature	LIKE	REGEXP / RLIKE
Syntax	Simple wildcards	Full regular expressions
Operators	%, _	^, $, [a-z], *, +
Performance	Faster, indexable	Slower, non-indexed
Flexibility	Limited	High
Case sensitivity	Based on collation	Case-insensitive by default

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🚀 Performance Tips

• Avoid using REGEXP on large datasets unless absolutely needed
• Prefer indexed LIKE 'prefix%' queries for performance
• Test regex patterns thoroughly before production usage
• Use REGEXP with filtered subsets (WHERE type = 'email' AND ...)

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📌 Summary – Recap & Next Steps

MySQL’s REGEXP, RLIKE, and NOT REGEXP provide powerful pattern-matching capabilities that go far beyond LIKE. Use them when you need flexible validation, complex filtering, or character-level matching.

🔍 Key Takeaways

• Use REGEXP or RLIKE for regular expression matching
• Use NOT REGEXP to find rows that do not match a pattern
• Escape characters carefully (e.g., \\. for .)
• REGEXP is case-insensitive unless BINARY is used
• Ideal for validating formats, filtering by patterns, and advanced searches

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❓ FAQ – REGEXP / RLIKE / NOT REGEXP

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❓ Are REGEXP and RLIKE the same?

✅ Yes. RLIKE is an alias for REGEXP.

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❓ Can I use REGEXP in WHERE clause?

✅ Yes. It’s designed for pattern matching in WHERE.

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❓ Is REGEXP case-sensitive?

❌ No, by default. Use BINARY for case-sensitive matching.

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❓ Can I use multiple regex conditions?

✅ Yes, using alternation or AND/OR:

REGEXP 'foo|bar' -- matches either

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❓ Is REGEXP slower than LIKE?

✅ Yes. REGEXP cannot use indexes, so it’s slower on large tables.

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