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freetds - Re: [freetds] select returns a " " character instead of ""

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  • From: michael.peppler AT bnpparibas.com
  • To: freetds AT lists.ibiblio.org
  • Subject: Re: [freetds] select returns a " " character instead of ""
  • Date: Thu, 6 Apr 2006 08:00:03 +0200

This isn't a freetds issue, but rather an MS-SQL (and Sybase) issue.

If you store an empty string into a non-null varchar column the db server
will in fact store a single space character. This is to distinguish the
"empty" string with the NULL value (which has 0 length).

Michael




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martin.rode AT programmfabrik.de@lists.ibiblio.org - 05/04/2006 20:00


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Subject: [freetds] select returns a " " character instead of ""


hi everybody,

i have found another problem, this time with a current version of php:

client:
* debian linux
* php 5.1.2
* tds 0.63 (debian unstable)

server:
* using microsoft sql server express 9.0.1399 on windows xp2

this following script. it should return a length of 0 for the string
data, but it returns 1.

i see the same problem with the php/sybase_* api.

--------------------------------
test_query2();


function test_query2() {
$dsn ="DRIVER={FreeTDS};SERVER=thepope;DATABASE=test";
$link2 = odbc_connect($dsn , 'sa', 'test' ) or die(odbc_errormsg() );
odbc_autocommit($link2, true);
odbc_exec($link2, "
IF EXISTS(SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE
TABLE_NAME = 'images') DROP TABLE [images];\n;
CREATE TABLE images (
name varchar(50),
data varchar(max)
);
");
$ins = "INSERT INTO images (name,data) VALUES ('henk','')";
odbc_exec($link2, $ins);

$sql = "SELECT data,datalength(data) as length FROM images";
$res = odbc_exec($link2, $sql);
$row = odbc_fetch_array($res);
echo "<pre>";
print_r($row);
print_r("STRLEN of 'data':".strlen($row[data]));
// this prints a length of 1, but it should be 0
}

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