DBI：bind_param将字符串转换为ntext - ＆gt; nvarchar（max）和ntext不兼容

Question

我有关于perl DBI的bind_param的问题。以下SQL有效：

my $sth = $dbh->prepare("SELECT id FROM table WHERE id = 'string'");
$sth->execute();

以下情况不是：

my $sth = $dbh->prepare("SELECT id FROM table WHERE id = ?");
$sth->execute('string');

上次查询导致的错误是[ODBC SQL Server Driver][SQL Server]The data types nvarchar(max) and ntext are incompatible in the equal to operator. (SQL-42000)。

似乎bind_param由execute调用，将'string'强制转换为ntext。我该如何解决这个问题？

Answer 1

考虑在SQL调用之前绑定值类型：

use DBI qw(:sql_types);

my $sth = $dbh->prepare( "SELECT id FROM table WHERE id = ?" );

my $key = 'string';
my $sth->bind_param( 1, $key, SQL_VARCHAR );

$sth->execute();