You might also find helpful doing a 2-table query if you really want to avoid doing them seperately. Here's a truncated example with postgres, with appropriate table definitions. 
pgunn=# \d entities
                                    Table "entities"
 Column |          Type          |                      Modifiers     
+                  
--------+------------------------+------------------------------------
+------------------
 eid    | integer                | not null default nextval('"entities
+_eid_seq"'::text)
 name   | character varying(120) | 
Primary key: entities_pkey
Unique keys: entities_name_key

pgunn=# \d friends
                             Table "friends"
 Column |  Type   |                      Modifiers                    
+   
--------+---------+---------------------------------------------------
+---
 e1     | integer | not null
 e2     | integer | not null
 rank   | integer | not null default nextval('"friends_rank_seq"'::tex
+t)
Unique keys: friends_rank_key

pgunn=# select rank,eid from friends,entities where friends.e1 = entit
+ies.eid;

[download]
Hope this helps

In reply to Re: Re: Re: Well Designed RDBMS by Improv
in thread Well Designed RDBMS by nothingmuch

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.