title: oracle SQLPLUS escape the & character
body: <p>As I find in the oracle doc, </p>
  
  <pre><code>SET ESCAPE:
   Defines an escape character you can use before the substitution character. The escape character instructs SQL*Plus to treat the substitution character as an ordinary character rather than as a request for variable substitution. The default escape character is a backslash (\).
  
  SET DEFINE:
   Defines the substitution character (by default the ampersand "&amp;") and turns substitution on and off.
  </code></pre>
  
  <p>before my query, should I do like this?:</p>
  
  <pre><code>SET DEFINE off
  select 'A&amp;B' from dual;
  SET DEFINE on
  </code></pre>
  
  <p>The use of set escape on is it necessary in my case?</p>