Trigger, record "old" is not assigned yet

<div class="Section1"><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt;
font-family:Arial">Hi,</span></font><p class="MsoNormal"><font face="Arial" size="2"><span style="font-size:10.0pt;
font-family:Arial"> </span></font><p class="MsoNormal"><font face="Arial" size="2"><span lang="EN-CA" style="font-size:
10.0pt;font-family:Arial">I’ve created a trigger BEFORE INSERT OR UPDATE on a table and, indeed, when the trigger is
raisedbefore insertion the record “old” is not assigned.  Is there a way to distinguish in the trigger procedure from
aninsert statement to an update statement?</span></font><p class="MsoNormal"><font face="Arial" size="2"><span
lang="EN-CA"style="font-size: 
10.0pt;font-family:Arial"> </span></font><p class="MsoNormal"><font face="Arial" size="2"><span lang="EN-CA"
style="font-size:
10.0pt;font-family:Arial">Regards,</span></font><p class="MsoNormal"><font face="Arial" size="2"><span lang="EN-CA"
style="font-size:
10.0pt;font-family:Arial"> </span></font><p class="MsoNormal"><font face="Arial" size="2"><span lang="EN-CA"
style="font-size:
10.0pt;font-family:Arial"> </span></font><p class="MsoNormal"><font face="Arial" size="2"><span lang="EN-CA"
style="font-size:
10.0pt;font-family:Arial">--</span></font><span lang="EN-CA"></span><p class="MsoNormal"><font face="Arial"
size="2"><spanlang="EN-CA" style="font-size: 
10.0pt;font-family:Arial">Daniel CAUNE</span></font><span lang="EN-CA"></span><p class="MsoNormal"><font face="Arial"
size="2"><spanlang="EN-CA" style="font-size: 
10.0pt;font-family:Arial">Ubisoft Online Technology</span></font><span lang="EN-CA"></span><p class="MsoNormal"><font
face="Arial"size="2"><span lang="EN-CA" style="font-size: 
10.0pt;font-family:Arial">(514) 490 2040 ext. 3613</span></font><span lang="EN-CA"></span><p class="MsoNormal"><font
face="TimesNew Roman" size="3"><span lang="EN-CA" style="font-size:12.0pt"> </span></font></div>