从不同的表和不同的数据库中获取数据

Question

I want to retrieve two different fields residing in different data bases. My db connection settings are this:

 define ('DB_HOST',     'ipaddress1');
 define ('DB_USER',     'username1');
 define ('DB_PASSWORD', 'password1');
 define ('DB_DATABASE', 'ecbooks');
 $db_wink = mysql_connect(DB_HOST, DB_USER, DB_PASSWORD, TRUE) or  die("Connection Error: " . mysql_error());
 mysql_select_db(DB_DATABASE) or die("Error connecting to Winkstore DB. " . mysql_error());

 // DB configuration parameters : magonwink
 define ('DB_REMOTE_HOST',     'ipaddress2');
 define ('DB_REMOTE_USER',     'username2');
 define ('DB_REMOTE_PASSWORD', 'password2');
 define ('DB_REMOTE_DATABASE', 'magsonwink');

 $db_magson = mysql_connect(DB_REMOTE_HOST, DB_REMOTE_USER,  DB_REMOTE_PASSWORD, TRUE) or die("Connection Error: " . mysql_error());
 mysql_select_db(DB_REMOTE_DATABASE, $db_magson) or die("Error connecting to magson wink DB. " . mysql_error());

 define ('CMS_DB_HOST',     'ipaddress3');
 define ('CMS_DB_USER',     'username3');
 define ('CMS_DB_PASSWORD', 'password3');
 define ('CMS_DB_DATABASE', 'mawinkcms');

 $db_rp = mysql_connect(CMS_DB_HOST, CMS_DB_USER, CMS_DB_PASSWORD, true) or die("Connection Error: " . mysql_error());
 mysql_select_db(CMS_DB_DATABASE, $db_rp) or die("Error connecting to DB. " . mysql_error());

but when I used this query

 SELECT ecbooks.user.user_name AS field1, mawinkcms.purchase.USER_NAME AS field2 FROM ecbooks.user,mawinkcms.purchase
 $result     = mysql_query($query, $db_wink) or die("Couldn't execute query: " . mysql_error());
 while($row = mysql_fetch_assoc($result)){
 $users[] = $row;
 }

I got an error could not execute the query. Thanks in advance.

Answer 1

You have to pass the correct link identifier to the mysql_query function as the second parameter: http://www.php.net/mysql_query

$ecbooks does not exist (based on the code you provided).

In your case if the table you want to access is in the ecbooks database, you have to pass $db_wink to mysql_query .

But since you are trying to access two different databases in the same query, you will have to connect to the database with a user that has access to both databases. Posting the actual error you get would also help.

ps: please stop usingng this extension to access MySQL. See here for details.

Answer 2

Firstly, when asking for help with an error, it's a good idea to include the error itself.

Secondly, your query doesn't appear to have a join condition, so you will get back the cartesian product if you do get it to go - that's probably not what you want.

Thirdly, when running a query, it runs against the database you connected to, regardless of whether you've connected to any others. So, in your example, you're running a query against $db_wink; the other two connections don't affect this at all.

For the query to work, the user who connected to $db_wink needs to have permissions on the databases ecbooks and mawinkcms, and mawinkcms must be running on the same server as ecbooks.

I'm guessing that either the permissions are not set up, or you're running them on different databases.