Generally speaking, placeholders are not appropriate in the FROM clause. I'm not sure which databases will even support prepare on a statement with a variable FROM. It also won't get you any performance benefit: the prepare'd statement would have to be re-planned everytime you executed it anyway.

You can have multiple statement handles, one for each table, but whether that's beneficial depends on what you're doing (the number of tables, the number of lookups, how long your program persists, etc.). Here's what I mean (warning, this is untested): 

 my %sth;
foreach my $tab (@checklists)
{
    # BTW, this SQL may be better written:
    #     select 1 from $tab where word = ?
    # if all you're testing for is existence...
    $sth{$tab} = $dbh->prepare("SELECT word from $tab where word = ?")
+;
}
# later...
foreach my $tab (@checklists)
{
    $sth{$tab}->execute($word);
    my $ret = $sth{$tab}->fetchrow_hashref();
}

[download]
I don't know whether MySQL will support having multiple prepared statements per handle. You'll have to check.

HTH

In reply to Re: Querying databases in a loop by VSarkiss
in thread Querying databases in a loop by schnarff

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