<h3>regexp_substr() function</h3>
Returns the portion of a string which matches a supplied regular expression.

<p><h4>Syntax</h4>
     regexp_substr(<i>string,regex</i>)</p>

<p><h4>Arguments</h4>
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<i>  string</i> &rarr; is string.  The input string.<br>
<i>  regex</i> &rarr; is string.  The regular expression to match against. Backslash characters must be double escaped (eg "\\s" to match a white space character). Non-greedy regular expressions are not supported.<br>

<p><h4>Example</h4>
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     regexp_substr('abc123','(\\d+)') &rarr; '123'</p>
