On Oct 22, 6:39 pm, [EMAIL PROTECTED] (Jenda Krynicky) wrote:
> > I am assigning a variable dynamically and using it in a query to
> > fetch values from my database. Here is the pseudo code...
>
> > ###########
> > my $string ;
> > my $q1 = "select * from bugs where target_milestone = ? and date
> > between ? and ?;
> > my $q2 = "select * from bugs where $string and target_milestone = ?
> > and date between ? and ?;
>
> > foreach my $q ($q1,$q2){
> > $stmt = $dbh->prepare($q1) or die ""; #####$dbh already has a valid
> > handle
> > $stmt->execute() or die "";
>
> > $string = "bug_id not in (1,2,3)"; #### 1,2,3 are eg. values which
> > i get after process $q1 and i #use it in $q2
> > }
>
> > ##################################
>
> > howver it happens that $string is not used in $q2 i.e. $q2 is executed
> > without taking into account the newly assigned value to $string and
> > instead using '';
>
> > Is it that perl compiles the statement statement beforehand and never
> > really substitutes it when foreach loop advances to use $q2.
>
> No it doesn't compile the statement. The catch is that string
> interpolation (the change from $varname to the value of the $varname
> in doublequoted strings) happens at the place you specify the
> doublequoted literal, not every time you used it:
>
> #!perl
> $x = 'original';
> $string = "The x='$x'.";
> $x = 'modified';
> print $string;
>
> If you want to change the value of the $q2 after it was assigned you
> have to put a mark there and replace that mark once you have the
> value you want to replace there. Something like
>
> my $string ;
> my $q1 = "select * from bugs where target_milestone = ? and date
> between ? and ?;
> my $q2 = "select * from bugs where ### and target_milestone = ? and
> date between ? and ?;
>
> foreach my $q_template ($q1,$q2){
> (my $q = $q_template) =~ s/###/$string/g;
>
> $stmt = $dbh->prepare($q1) or die "";
> #####$dbh already has a valid handle
> $stmt->execute() or die "";
>
> $string = "bug_id not in (1,2,3)";
> #### 1,2,3 are eg. values which i get after process $q1
> # and i use it in $q2
>
> }
>
> HTH, Jenda
>
> ===== [EMAIL PROTECTED] ===http://Jenda.Krynicky.cz=====
> When it comes to wine, women and song, wizards are allowed
> to get drunk and croon as much as they like.
> -- Terry Pratchett in Sourcery
Hey thanks Jendra... That is one helpfull logic.. I am sure gonna use
that.
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