my %where_type = (
    type1 => { _1_job => 'LIKE', _2_host_name => 'LIKE', _3_server => 'LIKE' },
    type2 => { _1_job => '=', _2_host_name => '=', _3_time_stamp => 'LIKE' },
    type3 => { _1_user_id => '!=', _2_user_id => 'LIKE', _3_time_stamp => '>' },
    );

sub build_sql
{
    my ( $type ) = @_;
    my $sql = "SELECT job,time_stamp,host_name,ip_address,server FROM cf_status_log";
    my @where_clauses = ();
    if ( exists( $where_type{$type} )) {
        for my $key ( sort keys %{$where_type{$type}} ) {
            ( my $fld = $key ) =~ s/^_\d_//;
            push @where_clauses, "$fld $where_type{$type}{$key} ?";
        }
    }
    $sql .= " where ".join( " and ", @where_clauses ) if @where_clauses;
}