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Re: DBI conditional insert (and things of those nature)

by Masem (Monsignor)
on Jan 25, 2002 at 23:47 UTC ( #141611=note: print w/ replies, xml ) Need Help??


in reply to DBI conditional insert (and things of those nature)

1) Most databases support unique id keys for tables. If you set up the employee database that the ID must be unique, and then try to insert a conflicting record, you'll get an error from DBI. Otherwise, it's probably just as easy to use either method; since rows() is a DBI level and not database level, it'll be portable anyway.

2) Instead of worrying about quotes, you should use placeholders in the DBI statement, such as:

$SQL = "INSERT INTO EMPLOYEE ( EMPLOYEE_NUMBER, FIRST_NAME, LAST_NAME, INFORMATION_DATE +) VALUES (?, ?, ?, SYSDATE)" +; $sth = $dbh->prepare($SQL); $sth->execute( $employee_number, $first_name, $last_name );
When you use placeholders, all variables are quoted appropriately to escape \' and \" constructs as well as other characters that might cuase the DB trouble. This is better than having to roll out your own.

Finally, not asked, but you're checking for errors in a very odd way. DBI statements don't die, so using eval won't catch errors. Instead, you should check the error status via the $DBI::errstr variable, and do this after every "prepare" and "execute" statement, such as

$SQL = "INSERT INTO EMPLOYEE ( EMPLOYEE_NUMBER, FIRST_NAME, LAST_NAME, INFORMATION_DATE +) VALUES (?, ?, ?, SYSDATE)" +; $sth = $dbh->prepare($SQL) or die $DBI::errstr; $sth->execute( $employee_number, $first_name, $last_name ) or die $D +BI::errstr;
Or, in your case, since you want to let the user know of a problem to the broswer, that execute can be written as:
if ( !$sth->execute( $employee_number, $first_name, $last_name ) ) { print "Could not insert into database: ", $DBI::errstr, "\n"; return; }
(or some control similar to that.)

-----------------------------------------------------
Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
"I can see my house from here!"
It's not what you know, but knowing how to find it if you don't know that's important


Comment on Re: DBI conditional insert (and things of those nature)
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Re: Re: DBI conditional insert (and things of those nature)
by lachoy (Parson) on Jan 26, 2002 at 00:36 UTC

    ++ on the placeholder issue (it's the only way to fly), but since the original code had RaiseError => 1 in the connect(), every DBI call that fails will issue a die. Extremely handy.

    Chris
    M-x auto-bs-mode

      True, though I'm not a big fan a RaiseError in production code (as it sorta hides what you are trying to do). But the original code had a bare execute() outside of an eval block, and this is the key step that would be need an error check if the unique ID route was taken.

      -----------------------------------------------------
      Dr. Michael K. Neylon - mneylon-pm@masemware.com || "You've left the lens cap of your mind on again, Pinky" - The Brain
      "I can see my house from here!"
      It's not what you know, but knowing how to find it if you don't know that's important

        I strongly disagree about RaiseError. It forces you to wrap every DBI call in an eval block. While people are free to ignore $@ after the block, those same people are much more likely to not do any error checking at all. The eval block at least turns on the siren that they should be doing something, much like try/catch blocks in Java.

        All MO, of course :-)

        Chris
        M-x auto-bs-mode

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