为什么 MySQL DATE_FORMAT 打印空白结果？
在过去的几个小时里，我一直在尝试使用 DATE_FORMAT 格式化 MySQL 时间戳，但它没有做任何事情！
Perl 代码：
use CGI;
use DBI;
my $q = new CGI;
# Database connection goes here
my $sth_select = $dbh->prepare(
"SELECT DATE_FORMAT(timestamp, '%m/%d/%y') FROM foo"
);
$sth_select->execute() || die "Unable to execute query: $dbh->errstr";
if (my $ref = $sth_select->fetchrow_hashref()) {
print $q->header;
print " TIME: $ref->{timestamp}";
exit;
}
结果
TIME:
它根本不打印格式化的时间，它是空白的！
当我尝试打印时间戳时，它不会打印任何内容，但如果我要删除 DATA_FORMAT 并只是简单地执行 SELECT timestamp FROM foo ，那么它会打印时间戳很好，虽然没有格式化。有人可以就这个问题提供他们的见解吗？
For the past couple of hours I've been trying to format a MySQL timestamp using DATE_FORMAT and it doesn't do anything!
Perl Code:
use CGI;
use DBI;
my $q = new CGI;
# Database connection goes here
my $sth_select = $dbh->prepare(
"SELECT DATE_FORMAT(timestamp, '%m/%d/%y') FROM foo"
);
$sth_select->execute() || die "Unable to execute query: $dbh->errstr";
if (my $ref = $sth_select->fetchrow_hashref()) {
print $q->header;
print " TIME: $ref->{timestamp}";
exit;
}
Results
TIME:
It doesn't print the formatted time at all, it is blank!
When I attempt to print the timestamp it doesn't print anything, but if I were to remove DATA_FORMAT and just simply do a SELECT timestamp FROM foo, then it prints the timestamp just fine, albeit not formatted though. Can somebody provide their insight on this matter, please?
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返回的散列具有数据库提供的键列标题。当使用这样的函数时，列标题实际上是“DATE_FORMAT(timestamp, '%m/%d/%y')”。
尝试将您的 SQL 修改为：
The hash returned has as keys column headers as provided by the database. When using a function like that, the column header is actually "DATE_FORMAT(timestamp, '%m/%d/%y')".
Try modifying your SQL to be: