Обсуждение: NULLIF problem
HELLO,<br /><br />I encounter an error if i use NULLIF with timestamp with time zone.<br />eq. dbtime=nullif(mytime,'')<br/><br />i want to null the value of field DBTIME if the variable mytime=" "<br /><br />DBTIME="timestamp with time zone" datatype <br /><br />error: column DBTIME is of type timestamp with time zone but expressionis of type text.<br /><br />What should i do?<br /><br />Thanks in advance...<br clear="all" /><br />-- <br />GeraMel E. Handumon<br />Application Programmer <br />PaySoft Solutions, Inc.<br />-----------------------------------------------------------------<br/>"Share your knowledge. It's a way to achieve immortality"- Dalai Lama
On Nov 27, 2007, at 21:04 , Gera Mel Handumon wrote: > I encounter an error if i use NULLIF with timestamp with time zone. > eq. dbtime=nullif(mytime,'') > > i want to null the value of field DBTIME if the variable mytime=" " > > DBTIME ="timestamp with time zone" datatype > > error: column DBTIME is of type timestamp with time zone but > expression is of type text. I believe the reason is that '' is not a valid timestamp value: think of it this way: IF mytime = '' THEN mytime := NULL; END IF; The first thing it needs to do is compare the mytime value with ''. As '' is not a valid timestamp value, it may be casing mytime to text. You'll run into problems if you're assigning a text value to a timestamp field (which happens after the initial comparison--and the cast--are done.) I think you may need to handle this is you middleware, or handle the IF THEN explicitly in a function. Maybe CASE would work: CASE WHEN mytime = '' THEN NULL ELSE CAST(mytime AS TIMESTAMP) END Michael Glaesemann grzm seespotcode net
On Nov 27, 2007, at 8:47 PM, Michael Glaesemann wrote: > > On Nov 27, 2007, at 21:04 , Gera Mel Handumon wrote: > >> I encounter an error if i use NULLIF with timestamp with time zone. >> eq. dbtime=nullif(mytime,'') >> >> i want to null the value of field DBTIME if the variable mytime=" " >> >> DBTIME ="timestamp with time zone" datatype >> >> error: column DBTIME is of type timestamp with time zone but >> expression is of type text. > > I believe the reason is that '' is not a valid timestamp value: > think of it this way: > > IF mytime = '' THEN > mytime := NULL; > END IF; > > The first thing it needs to do is compare the mytime value with ''. > As '' is not a valid timestamp value, it may be casing mytime to > text. You'll run into problems if you're assigning a text value to > a timestamp field (which happens after the initial comparison--and > the cast--are done.) > > I think you may need to handle this is you middleware, or handle > the IF THEN explicitly in a function. Maybe CASE would work: > > CASE WHEN mytime = '' THEN NULL > ELSE CAST(mytime AS TIMESTAMP) > END Why not just: UPDATE table SET mytime=NULL WHERE mytime=''; Erik Jones Software Developer | Emma® erik@myemma.com 800.595.4401 or 615.292.5888 615.292.0777 (fax) Emma helps organizations everywhere communicate & market in style. Visit us online at http://www.myemma.com
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
On Nov 28, 2007, at 14:00 , Erik Jones wrote: > Why not just: > > UPDATE table > SET mytime=NULL > WHERE mytime=''; If mytime is a timestamp field, it won't have any values ''. I believe the OP is updating mytime to a client-supplied value which is passing '' when it probably means NULL. Michael Glaesemann grzm seespotcode net