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[no subject]
I've read all through the postgres docs on this command and I'm still =
left lost. Can someone please explain to me in simple language how to =
use these commands or provide me with a link. I need it to live right =
now. Thanx.
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<DIV><FONT face=3DArial size=3D2>Hey guys, how u been. This is quite a =
newbie=20
question, but I need to ask it. I'm trying to wrap my mind around the =
syntax of=20
join and why and when to use it. I understand the concept of making a =
query go=20
faster by creating indexes, but it seems that when I want data from =
multiple=20
tables that link together the query goes slow. The slow is typically due =
to=20
expensive nested loops. The reason is, all my brain understands =
is:</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>select</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> =
tablea.data</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> =
tableb.data</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> =
tablec.data</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>from</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> tablea</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> tableb</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> tablec</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>where</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> tablea.pri_key =3D=20
tableb.foreign_key AND</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> tableb.pri_key =3D=20
tablec.foreign_key AND...</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>From what I read, it seems you can use =
inner/outer=20
right/left join on (bla) but when I see syntax examples I see that =
sometimes=20
tables are omitted from the 'from' section of the query and other times, =
no.=20
Sometimes I see that the join commands are nested and others, no and =
sometimes I=20
see joins syntax that only applies to one table. From what I understand =
join can=20
be used to tell the database the fast way to murge table data together =
to get=20
results by specifiying the table that has the primary keys and the table =
that=20
has the foreign keys.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I've read all through the postgres docs =
on this=20
command and I'm still left lost. Can someone please explain to me in =
simple=20
language how to use these commands or provide me with a link. I need it =
to live=20
right now. Thanx.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2> =
</FONT></DIV></BODY></HTML>
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