Perl MySQL查询访问超出数组';受约束
我有以下过程,用于同步两个MySQL表:Perl MySQL查询访问超出数组';受约束,mysql,perl,Mysql,Perl,我有以下过程,用于同步两个MySQL表: sub sync{ my %tables = ( 'sitematrix_test' => 'sitematrix_sites' ); while(($key, $value) = each(%tables)){ print "Matching columns $key : $value\n"; my @data; my $query = $db->p
sub sync{
my %tables = (
'sitematrix_test' => 'sitematrix_sites'
);
while(($key, $value) = each(%tables)){
print "Matching columns $key : $value\n";
my @data;
my $query = $db->prepare("
SELECT $key.* FROM $key LEFT JOIN $value ON
$key.site_id = $value.site_id WHERE $value.site_id IS NULL;
")
or die "Couldn't prepare statement: " . $db->errstr;
$query->execute()
or die "Couldn't execute statement: " . $query->errstr;
if($query->rows == 0){
print "No updates have been made for $key : $value";
}
else{
#read the matching records and print them out
while(@data = $query->fetchrow_array()){
print "@data\n";
}
}
$query->finish;
}
$db->disconnect;
}
它给出了以下错误:
Use of uninitialized value $data[3] in join or string at C:/Users/souzamor/workspace/Parser/synchronizer.pl line 69.
Use of uninitialized value $data[4] in join or string at C:/Users/souzamor/workspace/Parser/synchronizer.pl line 69.
Use of uninitialized value $data[5] in join or string at C:/Users/souzamor/workspace/Parser/synchronizer.pl line 69.
Use of uninitialized value $data[6] in join or string at C:/Users/souzamor/workspace/Parser/synchronizer.pl line 69.
有人能解释一下为什么它超出了数组的界限吗?您的数据库数据中有
NULL
s;它们在Perl中被转换为undef
。警告来自这一行:
print "@data\n";
在这里,您可以对数组进行字符串化。例如:
perl -Mwarnings -e '@foo=(1, 2, undef, 3); print "@foo\n"'
Use of uninitialized value $foo[2] in join or string at -e line 1.
1 2 3
如果您真的希望字符串化整个数组并每次打印它,一个简单的解决方案是将unde
s转换为空字符串:
while( my @data = map { defined($_) ? $_ : '' } $query->fetchrow_array() ) {
或者,如果您不需要打印每一行的所有数据,只需打印一个主键或一些您知道不会为
NULL
的内容,您也可以使用,而不是带有defined
的三元组。我不认为这样是正确的:while(my@data=map{defined?$\u:“”$query->fetchrow\u array())
@simbabque你能演示一下吗?@philippe,我更新了答案以解决地图中的语法问题。正如simbabque指出的,您还可以使用映射{$\uu/''}
。