 <p>Your regular expression is self-contradictory.</p> <p>You are bounding your pattern on word boundaries, and then including a non-word character in the string you're looking for. Since the '.' character isn't a word character, there will never be any strings that are delimited by word boundaries that include the '.'. </p> <p>Put another way, since the '.' is itself a word boundary, you are looking for [word-boundary][word-boundary][word], which cannot occur.</p> <p>Just take out the word boundaries in your REGEXP:</p> <pre><code>WHERE INET_NTOA(ip) REGEXP '\.111' </code></pre>