title: Input parameter validation for "optional" parameter
body: <p>I'm writing a SQL query and I'm stuck on the WHERE clause. What I'm trying to do with the last line is say, if no value has been input for the parameter, use the * argument (all values).</p>
  
  <pre><code>WHERE
  (REGEXP_INSTR('%params', '///') &gt; 0 AND REGEXP_LIKE(column1,'%params'))
  OR (REGEXP_INSTR('%params', '///') = 0 AND REGEXP_LIKE('%params'))
  OR (REGEXP_INSTR('%params', '') = 1 
  
  </code></pre>
  
  <p>It's the last line I'm having an issue with:</p>
  
  <pre><code>OR (REGEXP_INSTR('%params', '') = 1 
  </code></pre>
  
  <p>All runtime parameters must have a value, so this can't be NULL value. </p>
  
  <p>I'm not sure if ' ' will work, or might exibit some unwanted behaviour.</p>