我有一个最奇怪的问题，我对 SQL 的极其基础的知识一定是非常错误的，但我无法理解下面所示的行为。
我有这个文件 test.csv
id,field
A,0
B,1
C,2
D,"0"
E,"1"
F,"2"
G,
H,""
I," "
而这个测试代码:
#! /usr/bin/perl
use strict;
use warnings;
use DBI;
use Devel::VersionDump qw(dump_versions);
my $dbh = DBI->connect ("dbi:CSV:");
$dbh->{RaiseError} = 1;
$dbh->{TraceLevel} = 0;
my $i = 0;
foreach my $cond ("TRUE",
"field <> 0 AND field <> 1",
"field = 0 OR field = 1",
"NOT (field = 0 OR field = 1)",
"NOT field = 0 OR field = 1",
"field <> 0",
"NOT field <> 0",
) {
print "Condition #" . $i++ . " is $cond:\n";
my $sth = $dbh->prepare("SELECT * FROM test.csv WHERE $cond");
$sth->execute();
$sth->dump_results();
};
print "\n\n";
dump_versions();
运行时，这是输出:
Condition #0 is TRUE:
'A', '0'
'B', '1'
'C', '2'
'D', '0'
'E', '1'
'F', '2'
'G', ''
'H', ''
'I', ' '
9 rows
Condition #1 is field <> 0 AND field <> 1:
'C', '2'
'F', '2'
'G', ''
'H', ''
'I', ' '
5 rows
Condition #2 is field = 0 OR field = 1:
'A', '0'
'B', '1'
'D', '0'
'E', '1'
4 rows
Condition #3 is NOT (field = 0 OR field = 1):
'A', '0'
'B', '1'
'D', '0'
'E', '1'
4 rows
Condition #4 is NOT field = 0 OR field = 1:
'B', '1'
'C', '2'
'E', '1'
'F', '2'
'G', ''
'H', ''
'I', ' '
7 rows
Condition #5 is field <> 0:
'B', '1'
'C', '2'
'E', '1'
'F', '2'
'G', ''
'H', ''
'I', ' '
7 rows
Condition #6 is NOT field <> 0:
'A', '0'
'D', '0'
2 rows
Perl version: v5.16.3 on MSWin32 (C:\Program Files\Perl64\bin\perl.exe)
ActivePerl::Config - Unknown
ActiveState::Path - 1.01
AutoLoader - 5.73
C:::Program Files::Perl64::site::lib::sitecustomize.pl - Unknown
Carp - 1.26
Class::Struct - 0.63
Clone - 0.34
Config - Unknown
Config_git.pl - Unknown
Config_heavy.pl - Unknown
Cwd - 3.40
DBD::CSV - 0.41
DBD::File - 0.42
DBI - 1.631
DBI::DBD::SqlEngine - 0.06
DBI::SQL::Nano - 1.015544
Data::Dumper - 2.139
Devel::VersionDump - 0.02
DynaLoader - 1.14
Encode - 2.49
Encode::Alias - 2.16
Encode::Config - 2.05
Encode::Encoding - 2.05
Errno - 1.15
Exporter - 5.67
Exporter::Heavy - 5.67
Fcntl - 1.11
File::Basename - 2.84
File::Spec - 3.40
File::Spec::Unix - 3.40
File::Spec::Win32 - 3.40
File::stat - 1.05
IO - 1.25_06
IO::Dir - 1.1
IO::File - 1.16
IO::Handle - 1.33
IO::Seekable - 1.1
List::Util - 1.27
Math::BigFloat - 1.997
Math::BigInt - 1.998
Math::BigInt::Calc - 1.997
Math::Complex - 1.59
Math::Trig - 1.23
Params::Util - 1.07
SQL::Dialects::AnyData - 1.405
SQL::Dialects::Role - 1.405
SQL::Eval - 1.405
SQL::Parser - 1.405
SQL::Statement - 1.405
SQL::Statement::Function - 1.405
SQL::Statement::Functions - 1.405
SQL::Statement::Operation - 1.405
SQL::Statement::Placeholder - 1.405
SQL::Statement::RAM - 1.405
SQL::Statement::Term - 1.405
SQL::Statement::TermFactory - 1.405
SQL::Statement::Util - 1.405
Scalar::Util - 1.27
SelectSaver - 1.02
Symbol - 1.07
Text::CSV_XS - 1.07
Tie::Hash - 1.04
Time::HiRes - 1.9725
Win32 - 0.47
XSLoader - 0.16
base - 2.18
bytes - 1.04
constant - 1.25
integer - 1.00
overload - 1.18
overloading - 0.02
sort - 2.01
strict - 1.07
unicore::Heavy.pl - Unknown
unicore::lib::Perl::Word.pl - Unknown
unicore::lib::Perl::_PerlIDS.pl - Unknown
utf8 - 1.09
utf8_heavy.pl - Unknown
vars - 1.02
warnings - 1.13
warnings::register - 1.02
条件 #0 显示了完整的数据集并且很好。
条件 #1 只是一些复合条件并且工作正常。
条件 #2 是相反的条件(用于反转它的基本逻辑规则)，并且也能正常工作。
然而，条件#3 应该与#2 相反，因此等于#1，但结果与#2 相同:我无法理解这个 .
条件 #4 表明，省略括号，NOT 确实可以正常工作，但当然这个查询与之前的任何查询都不同。
条件 #5 和 #6 显示了一种情况，即 NOT 的行为完全符合人们的预期。
那么，为什么 NOT 在复合条件上表现得好像根本没有指定 NOT 一样？!
顺便说一句，我读了这篇可怕的帖子 Perl DBD::CSV - SQL Syntax - "AND" clause is not working properly并添加 Devel::VersionDump检查我是否有类似的问题，但在我看来，所有相关的软件包都是最新的。因此，我真的对此一无所知。
最佳答案
我确认这是 SQL::Parser 的错误:
'where_clause' => HASH(0x7f9686737480)
'arg1' => HASH(0x7f9686808248)
'arg1' => HASH(0x7f96866b50f8)
'fullorg' => 'field'
'type' => 'column'
'value' => 'field'
'arg2' => HASH(0x7f968588dfe0)
'fullorg' => 0
'type' => 'number'
'value' => 0
'neg' => 0
'nots' => HASH(0x7f96866b55d8)
empty hash
'op' => '='
'arg2' => HASH(0x7f9684498ce0)
'arg1' => HASH(0x7f96845fb798)
'fullorg' => 'field'
'type' => 'column'
'value' => 'field'
'arg2' => HASH(0x7f96866b5158)
'fullorg' => 1
'type' => 'number'
'value' => 1
'neg' => 0
'nots' => HASH(0x7f96866b55a8)
empty hash
'op' => '='
'neg' => 0
'nots' => HASH(0x7f9686808320)
empty hash
'op' => 'OR'
最上面的“否定”应该是 1。请在 https://rt.cpan.org/Dist/Display.html?Name=SQL-Statement 开票。 - 当您引用此线程时，测试用例已被证明:)
干杯，
延斯
关于sql - Perl、DBI 和 SQL : Why NOT does not work in some SQL queries?，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23488750/