Beefy Boxes and Bandwidth Generously Provided by pair Networks
Welcome to the Monastery

Comment on

( #3333=superdoc: print w/replies, xml ) Need Help??
Do hashtables in Perl always have keys?

An empty hash doesn't have any keys, but it's not the most useful case.

I am asked to create a hashtable from a database.But there is no unique values so that cant make any column as key.

I guess you haven't been asked to make a hash table just for the fun of it, but because somebody needs it. That somebody can tell you what the keys should be.

Note that even if there is no unique column in your database, there might a comination of columns that is unique, which you could then use as keys for the hash table (for example delimited by the zero-byte "\x0").

Or the user of the hash table might expect multiple values to be grouped as an array, or simply the first or last of the values.

A lil confused after hearing this requirement.

Then asked for clarification. But don't ask us, ask the one who made the requirements.

In reply to Re: Hash table by moritz
in thread Hash table by Ammu

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, 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, 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.
  • Log In?

    What's my password?
    Create A New User
    and all is quiet...

    How do I use this? | Other CB clients
    Other Users?
    Others pondering the Monastery: (4)
    As of 2017-08-23 20:15 GMT
    Find Nodes?
      Voting Booth?
      Who is your favorite scientist and why?

      Results (358 votes). Check out past polls.