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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Primary keys mean that there is one and only
one value for each record. In a resume table that you posted earlier that
means a person can have one and only one resume with name. I would
typically reverse this. The uid of a user doesn’t change, but it’s
name does, so you don’t want to be using name as a primary key. Use
uid as primary key and only put an index on name if you’re talking about
commonly looking up by or sorting by name. Primary keys usually imply an index
behind it but also add requiring one and only one value for each record. You
need the index to find out if a record already exists quickly. A primary key
typically can be thought of as an index with a uniqueness constraint. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Indexes generally dramatically improve
lookup time in large volume databases at the expense of taking a little longer
to write records. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I would strongly recommend that you pick
up a book on database design to learn these concepts. <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
support-bounces@drupal.org [mailto:support-bounces@drupal.org] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Austin Einter<br>
<b><span style='font-weight:bold'>Sent:</span></b> Thursday, March 17, 2011
4:26 AM<br>
<b><span style='font-weight:bold'>To:</span></b> development@drupal.org<br>
<b><span style='font-weight:bold'>Cc:</span></b> support@drupal.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [support] Doubt on Index
and Primary key</span></font><o:p></o:p></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>HI All<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>In .install file, in hook_schema unction, we are mentioning index field
and primary key field.<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>I am wondering, how to choose which one should be index and which
one should be primary key.<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Does that affect the performance (in search, add, delete of records).<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>What I am thinking at this point of time, my database will
contain job seekers name, mail-id, contact number, skill set (as comma
separated values) and resume.<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>For index purpose, I am thinking I will use '$user->uid' as Index
and and 'name' as primary key.<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>I am bit confused how it it is going to affect search/add/delete time
(assuming huge number of records in database) and also database management.<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Please guide me.<o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> <o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Regards<o:p></o:p></span></font></p>
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<p class=MsoNormal><st1:City w:st="on"><st1:place w:st="on"><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Austin</span></font></st1:place></st1:City><o:p></o:p></p>
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