Execute oracle sql query in PERL script while loop - oracle

Question

I am trying to execute an oracle sql query in while loop of a PERL script as follows --
my $dbh = DBI->connect( 'dbi:Oracle:'.$dbname,
$dbusername,
$pass,
{ PrintError => 0,
RaiseError => 1
}
) || die "Erreur lors de la connexion: $DBI::errstr";
print ("Connexion à la base de données $dbname avec $dbusername OK \n");
$requete = "select distinct to_char(date_appli,'yyyymmdd') from DATE_APPLI ".
"where frequence = 'Q' and actif = 1";
$sth_sql = $dbh->prepare($requete);
$sth_sql->execute();
#row=$sth_sql->fetchrow_array;
$datesitu=#row[0];
$sth_sql->finish;
print "La date de situation est $datesitu \n";
# SQL to get validation script and table names
$requete = "select SCRIPT_NAME, table_name from fdf_scripts";
$sth_sql = $dbh->prepare($requete);
$sth_sql->execute();
$sth_sql->bind_columns(undef, \$script_name, \$table_name);
while ($sth_sql->fetch()) {
$script_sql="$sql_path\\"."FDF_Test_scripts\\".$script_name.".sql"; #validation script path
$script_log="$log_path\\".$script_name.".log"; #log files path
$rep_file_name="$sql_path\\"."FDF_Test_scripts\\".$table_name.".sql"; #reports SQL path
$csv_file="$sql_path\\"."FDF_Test_scripts\\".$table_name.".csv"; #report CSV path
#Load data into validation tables using validation scripts
$CmdText="sqlplus -s $connect \#$script_sql $script_log";
print "Inserting data into table : $table_name \n";
#system ("$CmdText");
$col_sql = "select COLUMN_NAME from all_tab_cols where TABLE_NAME = upper(\'$table_name\')\n";
print "$col_sql\n";
$sth_sql = $dbh->prepare($col_sql);
$sth_sql->execute();
$sth_sql->bind_columns(undef, \$COLUMN_NAME);
while ($sth_sql->fetch()) {
print "$COLUMN_NAME\n";
}
if (open (my $fh, '<:encoding(UTF-8)', $script_log)){
while (my $line = <$fh>){
if ($line=~m/\bERROR\b/){
print "Error While Loading $table_name table Please Check log file for errors at: $script_log \n";
}
}
}
else {
warn "Could open file: $script_log \n"
}
}
in above code i am fetching table names from a table and then looping them to get the column names of each table which is present in that table.
The code got executed for one iteration of inner while loop but throw error for next iteration as below --
DBD::Oracle::st fetch failed: ERROR no statement executing (perhaps you need to call execute first) [for Statement "select COLUMN_N\
AME from all_tab_cols where TABLE_NAME = upper('FDF_Bond_validation_results')
I am not proficient in PERL and just started to using this and not sure how can i overcome this problem.
Please let me know if more information is required.

Answer 1

In the loop, the line $sth_sql = $dbh->prepare($col_sql); overwrite the content of the $sth_sql variable. The second time the loop run, the content of $sth_sql isn't the same and the statement that overwrote it has already been exhausted (trying to fetch from it again is what causes the error).
To correct this issue you should either use a different name for the second $sth_sql variable or simply declare the second $sth_sql variable with my to keep it inside the loop (see perldoc -f my).
Note: This solution has been identified by JGNI in the comment of the question. My role has only be to summarize the issue to provide a proper answer to this question.