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Home -> Community -> Mailing Lists -> Oracle-L -> RE: NULL value
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Mladen, from the class kit:
There is no index entry corresponding to a row that has all key colunmns that are NULL.
Bitmap indexes do store null entries in a way, since they store 1's and 0's - yes and no for all the values in the column.
So it seems to me, saying IS NULL or IS NOT NULL in a query does not use an index to retrieve the data, it becomes a full table scan, because it has nothing to work with.
Am I wrong?
Lisa Rutland Koivu
Oracle Database Administrator
Qode.com
4850 North State Road 7
Suite G104
Fort Lauderdale, FL 33319
V: 954.484.3191, x174 F: 954.484.2933 C: 954.658.5849
"The information contained herein does not express the opinion or position of Qode.com and cannot be attributed to or made binding upon Qode.com."
-----Original Message-----
From: Gogala, Mladen [mailto:MGogala_at_oxhp.com]
Sent: Tuesday, October 10, 2000 12:05 PM
To: Multiple recipients of list ORACLE-L
Subject: RE: NULL value
It's stored in the column because NULL != NULL. The only operators that can be applied to the NULL value are IS and IS NOT. Nothing else.
-----Original Message-----
Sent: Tuesday, October 10, 2000 7:26 AM
To: Multiple recipients of list ORACLE-L
Hi,
I have a logical question, any one who can make it clear.
create table a (x number(2) unique); insert into a values (null); 1 row created. insert into a values (null); 1 row created.
If null is a value, Why these null stored into table which have unique
constraint?
If null is not a VALUE then what it is?
Is there some special character for NULL?
If null is not a value why we have operators for null?
Regards
Muhammad Awais
System Developer
Paktel Ltd. Pakistan
Mob. 0303 7757077
(92-51) 111-222-111-282
-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: INET: awaisb_at_paktel.com Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-LReceived on Tue Oct 10 2000 - 15:17:18 CDT
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Gogala, Mladen INET: MGogala_at_oxhp.com Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from). You may
also send the HELP command for other information (like subscribing). ------_=_NextPart_001_01C032F7.1710E80E Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <HTML> <HEAD> <META HTTP-EQUIV=3D"Content-Type" CONTENT=3D"text/html; = charset=3Diso-8859-1"> <META NAME=3D"Generator" CONTENT=3D"MS Exchange Server version = 5.5.2650.12"> <TITLE>RE: NULL value</TITLE> </HEAD> <BODY> <P><FONT SIZE=3D2>Mladen, from the class kit:</FONT> </P> <P><FONT SIZE=3D2>There is no index entry corresponding to a row that = has all key colunmns that are NULL.</FONT> </P> <P><FONT SIZE=3D2>Bitmap indexes do store null entries in a way, since = they store 1's and 0's - yes and no for all the values in the = column.</FONT></P> <P><FONT SIZE=3D2>So it seems to me, saying IS NULL or IS NOT NULL in a = query does not use an index to retrieve the data, it becomes a full = table scan, because it has nothing to work with.</FONT></P> <P><FONT SIZE=3D2>Am I wrong?</FONT> </P> <P><FONT SIZE=3D2>Lisa Rutland Koivu</FONT> <BR><FONT SIZE=3D2>Oracle Database Administrator</FONT> <BR><FONT SIZE=3D2>Qode.com</FONT> <BR><FONT SIZE=3D2>4850 North State Road 7</FONT> <BR><FONT SIZE=3D2>Suite G104</FONT> <BR><FONT SIZE=3D2>Fort Lauderdale, FL 33319</FONT> </P> <P><FONT SIZE=3D2>V: 954.484.3191, x174</FONT> <BR><FONT SIZE=3D2>F: 954.484.2933 </FONT> <BR><FONT SIZE=3D2>C: 954.658.5849</FONT> <BR><FONT SIZE=3D2><A HREF=3D"http://www.qode.com" = TARGET=3D"_blank">http://www.qode.com</A></FONT> </P> <P><FONT SIZE=3D2>"The information contained herein does not = express the opinion or position of Qode.com and cannot be attributed to = or made binding upon Qode.com."</FONT></P> <BR> <P><FONT SIZE=3D2>-----Original Message-----</FONT> <BR><FONT SIZE=3D2>From: Gogala, Mladen [<A = HREF=3D"mailto:MGogala_at_oxhp.com">mailto:MGogala_at_oxhp.com</A>]</FONT> <BR><FONT SIZE=3D2>Sent: Tuesday, October 10, 2000 12:05 PM</FONT> <BR><FONT SIZE=3D2>To: Multiple recipients of list ORACLE-L</FONT> <BR><FONT SIZE=3D2>Subject: RE: NULL value</FONT> </P> <BR> <P><FONT SIZE=3D2>It's stored in the column because NULL !=3D NULL. The = only operators that</FONT> <BR><FONT SIZE=3D2>can be applied to the NULL value are IS and IS NOT. = Nothing else.</FONT> </P> <P><FONT SIZE=3D2>-----Original Message-----</FONT> <BR><FONT SIZE=3D2>Sent: Tuesday, October 10, 2000 7:26 AM</FONT> <BR><FONT SIZE=3D2>To: Multiple recipients of list ORACLE-L</FONT> </P> <BR> <P><FONT SIZE=3D2>Hi,</FONT> <BR><FONT SIZE=3D2>I have a logical question, any one who can make it = clear.</FONT> <BR> <FONT SIZE=3D2>create = table a (x number(2) unique);</FONT> <BR> <FONT SIZE=3D2>insert = into a values (null);</FONT> <BR> <FONT SIZE=3D2>1 row = created.</FONT> <BR> <FONT SIZE=3D2>insert = into a values (null);</FONT> <BR> <FONT SIZE=3D2>1 row = created.</FONT> <BR><FONT SIZE=3D2>Q:- I have a table 'A' have one field 'X' with = unique constraint, so a</FONT> <BR><FONT SIZE=3D2>unique index will be created for it. I inserted null = into this field two</FONT> <BR><FONT SIZE=3D2>times (or more then it). </FONT> </P> <P><FONT SIZE=3D2>If null is a value, Why these null stored into table = which have unique</FONT> <BR><FONT SIZE=3D2>constraint?</FONT> <BR><FONT SIZE=3D2>If null is not a VALUE then what it is?</FONT> <BR><FONT SIZE=3D2>Is there some special character for NULL?</FONT> <BR><FONT SIZE=3D2>If null is not a value why we have operators for = null?</FONT> </P> <P><FONT SIZE=3D2>Regards</FONT> </P> <P><FONT SIZE=3D2>Muhammad Awais</FONT> <BR><FONT SIZE=3D2>System Developer</FONT> <BR><FONT SIZE=3D2>Paktel Ltd. Pakistan</FONT> <BR><FONT SIZE=3D2>Mob. 0303 7757077</FONT> <BR><FONT SIZE=3D2>(92-51) 111-222-111-282</FONT> </P> <P><FONT SIZE=3D2>-- </FONT> <BR><FONT SIZE=3D2>Please see the official ORACLE-L FAQ: <A = HREF=3D"http://www.orafaq.com" = TARGET=3D"_blank">http://www.orafaq.com</A></FONT> <BR><FONT SIZE=3D2>-- </FONT> <BR><FONT SIZE=3D2>Author: </FONT> <BR><FONT SIZE=3D2> INET: awaisb_at_paktel.com</FONT> </P> <P><FONT SIZE=3D2>Fat City Network Services -- (858) = 538-5051 FAX: (858) 538-5051</FONT> <BR><FONT SIZE=3D2>San Diego, = California -- Public Internet = access / Mailing Lists</FONT> <BR><FONT = SIZE=3D2>---------------------------------------------------------------= -----</FONT> <BR><FONT SIZE=3D2>To REMOVE yourself from this mailing list, send an = E-Mail message</FONT> <BR><FONT SIZE=3D2>to: ListGuru_at_fatcity.com (note EXACT spelling of = 'ListGuru') and in</FONT> <BR><FONT SIZE=3D2>the message BODY, include a line containing: UNSUB = ORACLE-L</FONT> <BR><FONT SIZE=3D2>(or the name of mailing list you want to be removed = from). You may</FONT> <BR><FONT SIZE=3D2>also send the HELP command for other information =
(like subscribing).</FONT>
<BR><FONT SIZE=3D2>-- </FONT> <BR><FONT SIZE=3D2>Please see the official ORACLE-L FAQ: <A = HREF=3D"http://www.orafaq.com" = TARGET=3D"_blank">http://www.orafaq.com</A></FONT> <BR><FONT SIZE=3D2>-- </FONT> <BR><FONT SIZE=3D2>Author: Gogala, Mladen</FONT> <BR><FONT SIZE=3D2> INET: MGogala_at_oxhp.com</FONT> </P> <P><FONT SIZE=3D2>Fat City Network Services -- (858) = 538-5051 FAX: (858) 538-5051</FONT> <BR><FONT SIZE=3D2>San Diego, = California -- Public Internet = access / Mailing Lists</FONT> <BR><FONT = SIZE=3D2>---------------------------------------------------------------= -----</FONT> <BR><FONT SIZE=3D2>To REMOVE yourself from this mailing list, send an = E-Mail message</FONT> <BR><FONT SIZE=3D2>to: ListGuru_at_fatcity.com (note EXACT spelling of = 'ListGuru') and in</FONT> <BR><FONT SIZE=3D2>the message BODY, include a line containing: UNSUB = ORACLE-L</FONT>
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