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<p class="MsoNormal"><span style="color:#1F497D">We looked at this on the conference call and it seemed reasonable. Gareth, can you take a look at the attachment in the message below and let us know what you think?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> John Haug [mailto:johnhaug@exchange.microsoft.com]
<br>
<b>Sent:</b> Friday, March 30, 2012 4:25 PM<br>
<b>To:</b> SC34<br>
<b>Subject:</b> DR 12-0004 - SML: Decimal Precision of ISO 8601 Times<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi all –<o:p></o:p></p>
<p class="MsoNormal">I finally got my hands on ISO/IEC 9075 and looked up how it handles time precision. In short, there seem to be some context-specific concerns, but in general it merely provides for appending “(#)” to the decimal time value to indicate
the number of digits for fractional second precision. I didn’t see whether that is always the same as the number of digits that actually appear after the decimal point for a given time value, which would seem less than useful. I didn’t investigate this angle
further as it seemed ancillary to our DR.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">To document what we looked up and discussed during the teleconference, here are examples of the number of decimal digits for fractional time support for most typical cases/datatypes in a few of the larger databases:<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo2"><![if !supportLists]><span style="font-family:Symbol"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]>SQL Server 2012 Transact-SQL: 0-7 digits (default: 7)<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo2"><![if !supportLists]><span style="font-family:Symbol"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]>Oracle 9i, 10g, 11g: 0-9 digits (default: 6)<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo2"><![if !supportLists]><span style="font-family:Symbol"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]>MySQL 5: 0-6 digits, but discarded on storage (i.e., ephemeral/runtime use only)<o:p></o:p></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo2"><![if !supportLists]><span style="font-family:Symbol"><span style="mso-list:Ignore">·<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]>PostgreSQL 8, 9: 0-6 digits (default: ?)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I’m attaching as tracked changes draft 1 of the changes we discussed making (should, guidance/rationale). Given that 6+ digits is typical in the list above, I wonder if we ought to change the recommended number of digits from 3 to 6?
I’m also still not certain whether “with no more than X decimal places” or “with no fewer than X decimal places” or simply “with X decimal places” is the best choice. Any thoughts on that?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">John<o:p></o:p></p>
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