Help writing a piece of SQL

<div class="Section1"><p class="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew"">Hi, I would appreciate some help writing a piece of
SQL</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> </span></font><p class="MsoNormal"><font face="Courier New"
size="2"><spanlang="EN-GB" style="font-size:10.0pt;font-family:"Courier New"">PG803</span></font><p
class="MsoNormal"><fontface="Courier New" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier
New""> </span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew"">My table/data looks like this:</span></font><p
class="MsoNormal"><fontface="Courier New" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier
New""> </span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew"">     username     |            domain         |           
sendto           </span></font><p class="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"Courier
New"">+-------------+-------------------------------+------------------------------</span></font><p
class="MsoNormal"><fontface="Courier New" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier
New""> Postmaster      | intthit08.uk.rabbit.com   | root</span></font><p class="MsoNormal"><font face="Courier New"
size="2"><spanlang="EN-GB" style="font-size:10.0pt;font-family:"Courier New""> root             |
intthit08.uk.rabbit.com  | is-unix@rabbit.com</span></font><p class="MsoNormal"><font face="Courier New" size="2"><span
lang="EN-GB"style="font-size:10.0pt;font-family:"Courier New""> stoat.griffin    | trusting.co.uk            |
stoat.griffin@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> stoat.griffin    | trusting.com              |
stoat.griffin@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> stoat.griffin    | rusty.co.uk               |
stoat.griffin@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> stoat.griffin    | rusty.com                 |
stoat.griffin@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> matilda.clematis | trusting.com              |
matilda.clematis@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> matilda.clematis | trusting.co.uk            |
matilda.clematis@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> matilda.clematis | rusty.co.uk               |
matilda.clematis@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> matilda.clematis | rusty.com                 |
matilda.clematis@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> *                | trusting.com              |
rusty@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> *                | trusting.co.uk            |
rusty@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> *                | rusty.co.uk               |
rusty@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> *                | rusty.com                 |
rusty@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> *                | windoze.com               |
windoze@badger.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> *                | windoze.co.uk             |
windoze@badger.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> admin            | windoze.co.uk             |
matilda.clematis@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> admin            | windoze.com               |
matilda.clematis@rabbit.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> *                | saxon.co.uk               |
superR@uk.diamond.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> *                | saxon.com                 |
superR@uk.diamond.com</span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew""> </span></font><p class="MsoNormal"><font face="Courier New"
size="2"><spanlang="EN-GB" style="font-size:10.0pt;font-family:"Courier New""> </span></font><p class="MsoNormal"><font
face="CourierNew" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New"">The query will have
theusername and domain passed in as variables.</span></font><p class="MsoNormal"><font face="Courier New"
size="2"><spanlang="EN-GB" style="font-size:10.0pt;font-family:"Courier New""> </span></font><p class="MsoNormal"><font
face="CourierNew" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New"">If the username and
domainexist then return the sendto</span></font><p class="MsoNormal"><font face="Courier New" size="2"><span
lang="EN-GB"style="font-size:10.0pt;font-family:"Courier New""> </span></font><p class="MsoNormal"><font face="Courier
New"size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New"">The bit I’m struggling with is if
theusername doesn’t exist then return the sendto where the domain exists</span></font><p class="MsoNormal"><font
face="CourierNew" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New""> </span></font><p
class="MsoNormal"><fontface="Courier New" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier
New"">e.g. username=fred (this doesn’t exist) and domain=rusty.com then return <a
href="mailto:rusty@rabbit.com">rusty@rabbit.com</a>,<a
href="mailto:matilda.clematis@rabbit.com">matilda.clematis@rabbit.com</a>,<a
href="mailto:stoat.griffin@rabbit.com">stoat.griffin@rabbit.com</a></span></font><pclass="MsoNormal"><font
face="CourierNew" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New""> </span></font><p
class="MsoNormal"><fontface="Courier New" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier
New"">Anyhelp on this would very much appreciated; it’s been driving me mad for the last day.</span></font><p
class="MsoNormal"><fontface="Courier New" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier
New""> </span></font><pclass="MsoNormal"><font face="Courier New" size="2"><span lang="EN-GB"
style="font-size:10.0pt;font-family:"CourierNew"">Thanks</span></font><p class="MsoNormal"><font face="Courier New"
size="2"><spanlang="EN-GB" style="font-size:10.0pt;font-family:"Courier New""> </span></font><p class="MsoNormal"><font
face="CourierNew" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier New""> </span></font><p
class="MsoNormal"><fontface="Courier New" size="2"><span lang="EN-GB" style="font-size:10.0pt;font-family:"Courier
New"">Nigel</span></font><spanlang="EN-GB"></span></div><br /><br />Communications on or through ioko's computer
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