I hope this info can help you with your 2nd
question.

Off the top of my head there are aleast 3 ways
to check the table before you insert a new record.

way one) would be to define a unique constraint
on this table in the DBMS. This will prevent any
insertion of a record that is a duplicate.

way two) would be to define a before insert trigger
and have this trigger check for a duplicate.

way three) execute the query select count(*) into n from ...
and if n > 0 then the record exist.

--
Its like a dog that can sing and dance.
It's remarkable because it can do it.
Not that it can do it well.

In reply to Re: Handling Null or Undef values in DBI (and things of those nature)... by rbc
in thread Handling Null or Undef values in DBI (and things of those nature)... by data67

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.