comment on

It appears to me that your usertable looks something like this:

 id     username     branches
  1     vroom        gods,QandA,janitors
  2     merlyn       janitors
  3     Ovid         power users,janitors
  4     dws          power users,janitors,pmdev

This is violating the First Normal Form, which roughly states that no field of a table may contain multiple values. That's why we use Relational Databases in the first place, so that we don't have to use an outside Programming Language to split the values apart. Instead, you make another table, called branch or branches:

 id  name
  1  gods
  2  QandA
  3  janitors
  4  power users
  5  pmdev

Now, if a given user can only belong to one 'branch', then our user table might look like: (2nd Normal Form)

 id     username     branch_id
  1     vroom        1
  2     merlyn       3
  3     Ovid         4
  4     dws          4

If we need to pull out the branches, SQL to the rescue!

SELECT user.username, branch.name
FROM user
INNER JOIN branch ON user.branch_id = branch.id
[download]

However, a given user can belong to multiple branches, so we need employ the 3rd Normal Form. Start by removing the branch_id column from the user table, then create a new table - a 3rd table that will join Users to Branches: (user_branches)

user_id branch_id
   1        1
   1        2
   1        3    (vroom belongs to 1, 2, and 3)
  -------------
   2        3    (merlyn is a janitor)
  -------------
   3        4
   3        3    (Ovid is power user and janitor)
  -------------
   4        4
   4        3
   4        5

The SQL to join all three tables together is trickier, but the more you practice, the better you get. Here it is:

SELECT user.username, branch.name
FROM user
INNER JOIN user_branches ON user.id = user_branches.user_id
INNER JOIN branch ON user_branches.branch_id = branch.id
[download]

If you database tables are set up "properly", then you minimize the amount of work you have to do youself in Perl. Let the database do that work for you. :)

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)

In reply to OT: Database table design by jeffa
in thread AoH refs for setting HTML::Template loops by bradcathey

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