What does the dollar sign ($) mean in a MySQL REGEXP pattern?

Q: What does the dollar sign ($) mean in a MySQL REGEXP pattern?

In MySQL regular expressions, the dollar sign `$` is an anchor that matches the **end of a string**. It ensures that the pattern preceding the `$` occurs at the end of the string. **End Anchor:** `pattern$` matches strings that end with the specified pattern. **Position-Specific Matching:** Unlike simple substring matching, `$` ensures the match occurs at the very end of the string. **Combining with Character Classes:** You can use it with brackets, e.g., `[0-9]{4}$` matches strings ending with four digits. **Use in Validation:** Useful for validating formats that must end in a specific way, such as file extensions, postal codes, or numeric codes. When used in a SELECT query with REGEXP, `$` helps narrow down matches to strings ending with specific characters or patterns. SELECT email FROM users WHERE email REGEXP '\.com$'; SELECT phone FROM contacts WHERE phone REGEXP '00$';

Difficulty: 5/10

REGEXP syntax, pattern anchoring, MySQL regex behavior

Understanding the Dollar Sign ($) Symbol in MySQL REGEXP

In MySQL regular expressions, the dollar sign $ is an anchor that matches the end of a string. It ensures that the pattern preceding the $ occurs at the end of the string.

Key Points About the Dollar Sign ($) Symbol

1
End Anchor: pattern$ matches strings that end with the specified pattern.
2
Position-Specific Matching: Unlike simple substring matching, $ ensures the match occurs at the very end of the string.
3
Combining with Character Classes: You can use it with brackets, e.g., [0-9]{4}$ matches strings ending with four digits.

When used in a SELECT query with REGEXP, $ helps narrow down matches to strings ending with specific characters or patterns.

Example: Match Emails Ending with '.com'

Example: Match Phone Numbers Ending with '00'

Scenario Questions

0-2 years experience

1You need to write a query that returns rows where the email column ends with '.org'. How would you use the $ anchor in a MySQL REGEXP pattern to achieve that?
2If you run SELECT * FROM users WHERE username REGEXP 'admin$'; what rows will be matched and why?
3What would happen if you omitted the $ in the previous pattern—how would the result set change?

Follow-up Questions

How would you verify that your $‑anchored pattern works for edge cases like trailing whitespace?
What impact does using $ have on MySQL's ability to use indexes for REGEXP queries?
Can you describe a situation where $ might not behave as expected due to data encoding or collation?