PHP检查MS SQL数据库是否存在？

Question

I want to check if the database 'example' exist in my ms sql server
The code doesnt seem to work :/
Im getting,
sqlsrv_num_rows expects parameter 1 to be in resource

config.php

<?php
$userID=$_SESSION['userID']; 
$serverName = ''; 
$uid = '';   
$pwd = '';   
$connectionInfo = array( "UID"=>$uid,                            
                         "PWD"=>$pwd,                            
                         "Database"=>$userID); 

$conn = sqlsrv_connect( $serverName, $connectionInfo);


?>

file.php

<?php

function checkForUserDB($userID){

    $_SESSION['userID'] = $userID;
    include('config.php');
    $sql="SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME ='".$userID."'";
    $result=sqlsrv_query($conn,$sql, array(), array( "Scrollable" => 'static' ));
    $count=sqlsrv_num_rows($result);
    if($count==1){

        echo "Database Exist!";
    }
    else{
        echo "Database does not exist!";

    }
}



checkForUserDB('example');

?>

Answer 1

You have several problems:

• First, you are not checking the return value of sqlsrv_query(), which returns FALSE if the query fails, and in that case you're passing FALSE to sqlsrv_num_rows(), which seems to be your first problem. You have to do something like this:

  $result=sqlsrv_query($conn, $sql, array(), array( "Scrollable" => 'static' ));
  if ($result===false) {
    // only print SQL error while debugging, in production log the error to a file
    exit("Error executing query: ".sqlsrv_errors());
  }
  else {
    $count=sqlsrv_num_rows($result);
    // rest of your code
  }
  

• Then, you are using the wrong field of INFORMATION_SCHEMA.SCHEMATA, in SQL Server the database is CATALOG but you are checking SCHEMA_NAME which is, well, the schema, being the default schema of SQL Server dbo.

• Finally, you are trying to check if a database exists trying to connect in first place to that database, so if the database doesn't exists the connection fails, and since you aren't checking the result of sqlsrv_connect() this is probably the cause of the failed sqlsrv_query() later. You have to connect to a database that always exists, not to the database that you want to check:

  $connectionInfo = array( "UID"=>$uid,                            
                           "PWD"=>$pwd,                            
                           "Database"=>'YourMainDatabase'; // this database must exists