Re: NULLIF problem

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От Gera Mel Handumon
Тема Re: NULLIF problem
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Msg-id 474404120711290143g6ef15a73j9363b2b95882f043@mail.gmail.com
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Ответ на Re: NULLIF problem  (Michael Glaesemann <grzm@seespotcode.net>)
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Thanks!<br /><br /><div class="gmail_quote">On Nov 28, 2007 10:47 AM, Michael Glaesemann <<a
href="mailto:grzm@seespotcode.net">grzm@seespotcode.net</a>>wrote:<br /><blockquote class="gmail_quote"
style="border-left:1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div class="Ih2E3d"><br
/>OnNov 27, 2007, at 21:04 , Gera Mel Handumon wrote:<br /><br />> I encounter an error if i use NULLIF with
timestampwith time zone.<br />> eq. dbtime=nullif(mytime,'')<br />><br />> i want to null the value of field
DBTIMEif the variable mytime=" " <br />><br />> DBTIME ="timestamp with time zone" datatype<br />><br />>
error:column DBTIME is of type timestamp with time zone but<br />> expression is of type text.<br /><br /></div>I
believethe reason is that '' is not a valid timestamp value: think <br />of it this way:<br /><br />IF mytime = ''
THEN<br/>   mytime := NULL;<br />END IF;<br /><br />The first thing it needs to do is compare the mytime value with
''.<br/>As '' is not a valid timestamp value, it may be casing mytime to <br />text. You'll run into problems if you're
assigninga text value to a<br />timestamp field (which happens after the initial comparison--and the<br />cast--are
done.)<br/><br />I think you may need to handle this is you middleware, or handle the <br />IF THEN explicitly in a
function.Maybe CASE would work:<br /><br />CASE WHEN mytime = '' THEN NULL<br />      ELSE CAST(mytime AS TIMESTAMP)<br
/>    END<br /><font color="#888888"><br />Michael Glaesemann<br />grzm seespotcode net <br /><br /><br
/></font></blockquote></div><br/><br clear="all" /><br />-- <br />Gera Mel E. Handumon<br />Application Programmer<br
/>PaySoftSolutions, Inc.<br />-----------------------------------------------------------------<br />"Share your
knowledge.It's a way to achieve immortality" - Dalai Lama  

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