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#! /usr/bin/perl -w # This script checks which style of WHERE clause(s) will support both # null and non-null values. Refer to the NULL Values sub-section # of the "Placeholders and Bind Values" section in the DBI # documention for more information on this issue. The clause styles # and their numbering (0-6) map directly to the examples in the # documentation. # # To use this script: # # 1) If you are not using the DBI_DSN env variable, then update the # connect method arguments to support your database engine and # database, and remove the nearby check for DBI_DSN. # 2) Set PrintError to 1 in the connect method if you want see the # engine's reason WHY your engine won't support a particular # style. # 3) If your database does not support NULL columns by default # (e.g. Sybase) find and edit the CREATE TABLE statement # accordingly. # 4) To properly test style #5, you need the capability to create the # stored procedure SP_ISNULL that acts as a function: it tests its # argument and returns 1 if it is null, 0 otherwise. For example, # using Informix IDS engine, a definition would look like: # # CREATE PROCEDURE SP_ISNULL (arg VARCHAR(32)) RETURNING INTEGER; # IF arg IS NULL THEN RETURN 1; # ELSE RETURN 0; # END IF; # END PROCEDURE; # # Warning: This script will attempt to create a table named by the # $tablename variable (default dbi__null_test_tmp) and WILL DESTROY # any pre-existing table so named. use strict; use DBI; # The array represents the values that will be stored in the char column of our table. # One array element per row. # We expect the non-null test to return row 3 (Marge) # and the null test to return rows 2 and 4 (the undefs). my $homer = "Homer"; my $marge = "Marge"; my @char_column_values = ( $homer, # 1 undef, # 2 $marge, # 3 undef, # 4 ); # Define the SQL statements with the various WHERE clause styles we want to test # and the parameters we'll substitute. my @select_clauses = ( {clause=>qq{WHERE mycol = ?}, nonnull=>[$marge], null=>[undef]}, {clause=>qq{WHERE NVL(mycol, '-') = NVL(?, '-')}, nonnull=>[$marge], null=>[undef]}, {clause=>qq{WHERE ISNULL(mycol, '-') = ISNULL(?, '-')}, nonnull=>[$marge], null=>[undef]}, {clause=>qq{WHERE DECODE(mycol, ?, 1, 0) = 1}, nonnull=>[$marge], null=>[undef]}, {clause=>qq{WHERE mycol = ? OR (mycol IS NULL AND ? IS NULL)}, nonnull=>[$marge,$marge], null=>[undef,undef]}, {clause=>qq{WHERE mycol = ? OR (mycol IS NULL AND SP_ISNULL(?) = 1)}, nonnull=>[$marge,$marge], null=>[undef,undef]}, {clause=>qq{WHERE mycol = ? OR (mycol IS NULL AND ? = 1)}, nonnull=>[$marge,0], null=>[undef,1]}, ); # This is the table we'll create and use for these tests. # If it exists, we'll DESTROY it too. So the name must be obscure. my $tablename = "dbi__null_test_tmp"; # Remove this if you are not using the DBI_DSN env variable, # and update the connect statement below. die "DBI_DSN environment variable not defined" unless $ENV{DBI_DSN}; my $dbh = DBI->connect(undef, undef, undef, { RaiseError => 0, PrintError => 1 } ) \|\| die DBI->errstr; printf "Using %s, db version: %s\n", $ENV{DBI_DSN} \|\| "connect arguments", $dbh->get_info(18) \|\| "(unknown)"; my $sth; my @ok; print "=> Drop table '$tablename', if it already exists...\n"; do { local $dbh->{PrintError}=0; $dbh->do("DROP TABLE $tablename"); }; print "=> Create table '$tablename'...\n"; $dbh->do("CREATE TABLE $tablename (myid int NOT NULL, mycol char(5))"); # Use this if your database does not support NULL columns by default: #$dbh->do("CREATE TABLE $tablename (myid int NOT NULL, mycol char(5) NULL)"); print "=> Insert 4 rows into the table...\n"; $sth = $dbh->prepare("INSERT INTO $tablename (myid, mycol) VALUES (?,?)"); for my $i (0..$#char_column_values) { my $val = $char_column_values[$i]; printf " Inserting values (%d, %s)\n", $i+1, $dbh->quote($val); $sth->execute($i+1, $val); } print "(Driver bug: statement handle should not be Active after an INSERT.)\n" if $sth->{Active}; # Run the tests... for my $i (0..$#select_clauses) { my $sel = $select_clauses[$i]; print "\n=> Testing clause style $i: ".$sel->{clause}."...\n"; $sth = $dbh->prepare("SELECT myid,mycol FROM $tablename ".$sel->{clause}) or next; print " Selecting row with $marge\n"; $sth->execute(@{$sel->{nonnull}}) or next; my $r1 = $sth->fetchall_arrayref(); my $n1_rows = $sth->rows; my $n1 = @$r1; print " Selecting rows with NULL\n"; $sth->execute(@{$sel->{null}}) or next; my $r2 = $sth->fetchall_arrayref(); my $n2_rows = $sth->rows; my $n2 = @$r2; # Complain a bit... print "\n=>Your DBD driver doesn't support the 'rows' method very well.\n\n" unless ($n1_rows == $n1 && $n2_rows == $n2); # Did we get back the expected "n"umber of rows? # Did we get back the specific "r"ows we expected as identifed by the myid column? if ( $n1 == 1 # one row for Marge && $n2 == 2 # two rows for nulls && $r1->[0][0] == 3 # Marge is myid 3 && $r2->[0][0] == 2 # NULL for myid 2 && $r2->[1][0] == 4 # NULL for myid 4 ) { print "=> WHERE clause style $i is supported.\n"; push @ok, "\tStyle $i: ".$sel->{clause}; } else { print "=> WHERE clause style $i returned incorrect results.\n"; if ($n1 > 0 \|\| $n2 > 0) { print " Non-NULL test rows returned these row ids: ". join(", ", map { $r1->[$_][0] } (0..$#{$r1}))."\n"; print " The NULL test rows returned these row ids: ". join(", ", map { $r2->[$_][0] } (0..$#{$r2}))."\n"; } } } $dbh->disconnect(); print "\n"; print "-" x 72, "\n"; printf "%d styles are supported:\n", scalar @ok; print "$_\n" for @ok; print "-" x 72, "\n"; print "\n"; print "If these results don't match what's in the 'Placeholders and Bind Values'\n"; print "section of the DBI documentation, or are for a database that not already\n"; print "listed, please email the results to dbi-users\@perl.org. Thank you.\n"; exit 0;