<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
</head>
<body>
Dear DAL members,<br>
<br>
Here is a Proposed Erratum aiming to fix ADQL-2.0 about the usage of
<font face="monospace">NULL</font> values. Apart from the constraint
`<font face="monospace">IS [NOT] NULL</font>`, it was not possible
to use the special value <font face="monospace">NULL</font>
anywhere.<br>
<br>
This problem has been raised thanks to the development of the ADQL
validator for the official IVOA grammar: <a moz-do-not-send="true"
href="https://github.com/ivoa/lyonetia/pull/16#issuecomment-1406523355"
class="moz-txt-link-freetext">https://github.com/ivoa/lyonetia/pull/16#issuecomment-1406523355</a>
One of the examples that highlighted this issue is:<br>
<br>
<font face="monospace">SELECT x FROM y WHERE Point(NULL, 2,
3)=x</font><br>
<br>
Allowing <font face="monospace">NULL</font> instead of a literal,
expression or column name is anyway already supported in most of the
existing ADQL parsers and TAP services (DACHS and CADC) and is
completely supported by major DBMS.<br>
<br>
Here is the link toward this Proposed Erratum:<br>
<br>
<blockquote><a moz-do-not-send="true"
href="https://wiki.ivoa.net/twiki/bin/view/IVOA/ADQL20Err4"
class="moz-txt-link-freetext">https://wiki.ivoa.net/twiki/bin/view/IVOA/ADQL20Err4</a><br>
</blockquote>
<br>
Don't hesitate to comment.<br>
<br>
Cheers,<br>
Grégory<br>
</body>
</html>