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PostgreSQL: 8.2
=20
When you create a foreign key to a table is there an index that is
created on the foreign key automatically?
=20
Example:
Table A has a field called ID.
=20
Table B has a field called fk_a_id which has a constraint of being a
foreign key to table A to field ID.
=20
Is there an index automatically created on field fk_a_id in table B when
I create a foreign key constraint?
=20
=20
I assume yes. But I wanted to check. I did not see it specifically
mentioned in the documentation.
=20
I also see "CREATE TABLE / PRIMARY KEY will create implicit index" when
creating a primary key but I don't see any similar statement when
creating a foreign key.
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Thanks,
=20
Lance Campbell
Project Manager/Software Architect
Web Services at Public Affairs
University of Illinois
217.333.0382
http://webservices.uiuc.edu
=20
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<div class=3DSection1>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>PostgreSQL: 8.2<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>When you create a foreign key to a table is there an =
index
that is created on the foreign key =
automatically?<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Example:<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Table A has a field called =
ID.<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Table B has a field called fk_a_id which has a =
constraint of
being a foreign key to table A to field ID.<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Is there an index automatically created on field =
fk_a_id in
table B when I create a foreign key =
constraint?<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>I assume yes. But I wanted to check. I =
did not
see it specifically mentioned in the =
documentation.<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>I also see “CREATE TABLE / PRIMARY KEY will =
create
implicit index” when creating a primary key but I don’t see =
any similar
statement when creating a foreign key.<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Thanks,<o:p></o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Lance Campbell</span></font><o:p></o:p></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Project Manager/Software =
Architect</span></font><o:p></o:p></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>Web Services at Public =
Affairs</span></font><o:p></o:p></p>
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w:st=3D"on"><font size=3D2
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1:PlaceType><font
size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;font-family:Arial'> of <st1:PlaceName
=
w:st=3D"on">Illinois</st1:PlaceName></span></font></st1:place><o:p></o:p>=
</p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>217.333.0382</span></font><o:p></o:p></p>
<p class=3DMsoNormal><font size=3D2 face=3DArial><span =
style=3D'font-size:10.0pt;
font-family:Arial'>http://webservices.uiuc.edu</span></font><o:p></o:p></=
p>
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