pdo_sqlsrv: how to recognize if fetch “false” is an error or empty recordset?

问题

The fetch method returns false both if the recordset is empty and if there is an actual error. The method described here allows you to easily recognize what is happening:

ensure that PDO fetch method result "false" is a error or empty result

It works well with pdo_mysql, however pdo_sqlsrv throws an error even when the recordset is empty. Is this the intended behaviour? Is it possible to avoid those errors?

EDIT: the error is "There are no more rows in the active result set" and it is produced when you try to fetch a recordset which is already completely fetched. This not happens with pdo_mysql, which just returns false.

EDIT 2: I have finally understood the problem more in details: the first time you fetch an empty recordset you get FALSE, then, if you fetch again, you get an error. This doesn't happen with pdo_mysql (and I am pretty sure it doesn't happen with PDO pgsql and sqlite either): you still get false without producing errors.

Here is a simplified version of the code:

// sqlsrv connection
$conn = new PDO("sqlsrv:Server=....;Database=....", "user", "password", array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION ));

// mysql connection
// $conn = new PDO('mysql:host=....;dbname=....', 'user', 'password', array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));

$sql = "drop table if exists test;";
$res = $conn->query($sql);

$sql = "create table test (name varchar(10));";
$res = $conn->query($sql);

$sql = "insert into test (name) values ('Alice');";
$res = $conn->query($sql);

$sql = "select * from test";
$res = $conn->query($sql);

// fetch first record
$row = fetch_row_db($res);
var_dump($row);

// fetch again
$row = fetch_row_db($res);
var_dump($row);

// fetch again
$row = fetch_row_db($res);
var_dump($row);

function fetch_row_db(&$res)
{
    try {
        return $res->fetch();
    }
    catch(PDOException $e){
        echo 'Error during record fetching.';
        exit();
    }
}

OUTPUT:

MySQL
array(2) { ["name"]=> string(5) "Alice" [0]=> string(5) "Alice" } bool(false) bool(false)

sqlsrv
array(2) { ["name"]=> string(5) "Alice" [0]=> string(5) "Alice" } bool(false) Error during record fetching.

来源：https://stackoverflow.com/questions/53063059/pdo-sqlsrv-how-to-recognize-if-fetch-false-is-an-error-or-empty-recordset

标签

php

sql-server

pdo