Why do I get "Conversion failed when converting date and/or time from character string" when subtracting a number from GETDATE()? - sql-server

Question

I cannot figure out what I am doing incorrect here. I have the following values for these variables.
my $sql = qq~
SELECT COUNT(*)
FROM tableName u
WHERE 1=1 AND u.ManufacturerPartNumber IN ('X','Y','Z')
AND CAST(u.InspectionStartDate AS DATETIME) > (GETDATE() - ?)
~;
my $argsRef->{lookBack} = 30;
And when I try to run a selectrow_array on the sql like such:
my $qnCount = $dbh->selectrow_array($sql, undef, $argsRef->{lookBack});
I get the following error:
DBD::ODBC::db selectrow_array failed: [Microsoft][ODBC SQL Server Driver][SQL Server]Conversion failed when converting date and/or time from character string. (SQL-22007) [for Statement "
SELECT COUNT(*)
FROM tableName u
WHERE 1=1 AND u.ManufacturerPartNumber IN ('X','Y','Z')
AND CAST(u.InspectionStartDate AS DATETIME) > (GETDATE() - ?)
"]
So, it is my understanding that the third parameter in the selectrow_array call from a database handle should be the bind variables. Yet, they seem not to be binding....
the database handle is created as such:
my $dbh = DBI->connect_cached("dbi:ODBC:$dsn", undef, undef, {
PrintError => 0,
RaiseError => 1,
ShowErrorStatement => 1,
LongReadLen => 500000,
})
$dsn is the correct DSN but not shown for various reasons, but we know it works due the error message coming back from SQL Server.
Any idea what I am doing wrong?
Thanks in advance for your help.

Answer 1

First, a shout out to ThisSuitIsBlackNot for pointing out that the problem. I made the assumption that the DBI/driver would be able to determine the value type. That was wrong. So, I explicitly stated the type:
$sth = $dbh->prepare($sql);
$sth->bind_param( 1, ($argsRef->{lookBack} * -1), { TYPE => SQL_INTEGER });
$sth->execute();
my $qnCount = $sth->fetchrow_array();
This allowed it to go through as an integer and the SQL ran without problem.
In case you were wondering why I am multiplying by -1, is because I changed the query to use DATEADD:
SELECT COUNT(*)
FROM tableName u
WHERE 1=1 AND u.ManufacturerPartNumber IN ('x')
AND CAST(u.InspectionStartDate AS DATETIME) > DATEADD(dd, ?, GETDATE())
Although there seems to be some continuing discussion in regards to its use, it is working here.
Thank you all for your help.