Quick Learning PHP database files using _php tutorial

PHP is still more commonly used, so I studied the PHP database file, here to take out and share with you, hope to be useful to everyone. We will see an application in which each table is in a separate database. It is reasonable to do so in a very large database, but for a generic application, this level of fragmentation is not required. In addition, relational queries cannot be executed across databases, which can affect the overall idea of using relational databases, not to mention the difficulty of managing tables across multiple databases. So, what should multiple databases look like? First, you need some data. Listing 1 shows such data divided into 4 files.

Listing 1. PHP Database files

 
 

  
  

  
Files.sql:
  
  

  
CREATE TABLE Files (
  
  

  
ID Mediumint,
  
  

  
USER_ID Mediumint,
  
  

  
Name TEXT,
  
  

  
Path TEXT
  
  

  
);
  
  

  

  
  

  
Load_files.sql:
  
  

  
INSERT into Files VALUES (1, 1, ' test1.jpg ', ' files/test1.jpg ');
  
  

  
INSERT into Files VALUES (2, 1, ' test2.jpg ', ' files/test2.jpg ');
  
  

  

  
  

  
Users.sql:
  
  

  
DROP TABLE IF EXISTS users;
  
  

  
CREATE TABLE Users (
  
  

  
ID Mediumint,
  
  

  
Login TEXT,
  
  

  
Password TEXT
  
  

  
);
  
  

  

  
  

  
Load_users.sql:
  
  

  
INSERT into Users VALUES (1, ' Jack ', ' Pass ');
  
  

  
INSERT into Users VALUES (2, ' Jon ', ' Pass ');
 
 

There are a number of ways you can create database design, database access, and database-based PHP business logic code, but ultimately end up with errors and how to fix them when you encounter these problems. In the multi-database version of these files, you should load the SQL statements into one database, and then load the users SQL statements into another database. The PHP code used to query the database for files associated with a particular user is shown below. The Get_user function connects to the database that contains the user table and retrieves the ID of the given user. The Get_files function connects to a file table and retrieves the file rows associated with a given user. A better way to do all of these things is to load the data into a database and then execute the query, such as the following query.

Listing 2. PHP Database File getfiles.php

 
 

  
  

  
 
  
  

  
Require_once ("db.php");
  
  

  

  
  

  
function Get_user ($name)
  
  

  
{
  
  

  
$ DSN  =  ' Mysql://root:password@localhost/bad_multi1 ' ; 
  
  

  
$ DB =& db::connect ($DSN, Array ()); 
  
  

  
if (Pear::iserror ($db)) {die ($db->getmessage ());}
  
  

  

  
  

  
$ Res = $db->query ("Select ID from users WHERE  login=?", array ($name)); 
  
  

  
$ UID  =  NULL ; 
  
  

  
While ($res->fetchinto ($row)) {$uid  = $row [0];} 
  
  

  

  
  

  
return $uid;
  
  

  
}
  
  

  

  
  

  
function Get_files ($name)
  
  

  
{
  
  

  
$ UID  =  Get_user ($name); 
  
  

  

  
  

  
$ rows  =  Array (); 
  
  

  

  
  

  
$ DSN  =  ' Mysql://root:password@localhost/bad_multi2 ' ; 
  
  

  
$ DB =& db::connect ($DSN, Array ()); 
  
  

  
if (Pear::iserror ($db)) {die ($db->getmessage ());}
  
  

  

  
  

  
$ Res = $db->query ("select * from Files WHERE  user_id=?", array ($uid)); 
  
  

  
while ($res->fetchinto ($row)) {$rows [] = $row;}
  
  

  
return $rows;
  
  

  
}
  
  

  

  
  

  
$ Files  =  Get_files (' Jack '); 
  
  

  

  
  

  
Var_dump ($files);
  
  

  
? >
 
 

Listing 3. getfiles_good.php

 
 

  
  

  
 
  
  

  
Require_once ("db.php");
  
  

  

  
  

  
function Get_files ($name)
  
  

  
{
  
  

  
$ rows  =  Array (); 
  
  

  

  
  

  
$ DSN  =  ' Mysql://root:password@localhost/good_multi ' ; 
  
  

  
$ DB =& db::connect ($DSN, Array ()); 
  
  

  
if (Pear::iserror ($db)) {die ($db->getmessage ());}
  
  

  

  
  

  
$ Res = $db->query ("Select files.* from Users, files WHERE
  
  

  
Users.login =? and  users.id=files. user_id ",
  
  

  
Array ($name));
  
  

  
while ($res->fetchinto ($row)) {$rows [] = $row;}
  
  

  

  
  

  
return $rows;
  
  

  
}
  
  

  

  
  

  
$ Files  =  Get_files (' Jack '); 
  
  

  

  
  

  
Var_dump ($files);
  
  

  
? >
 
 

The code is not only shorter, but also easier to understand and efficient. Instead of executing two queries, we execute a query. Although the problem may sound far-fetched, in practice we usually conclude that all tables should be in the same database, unless there is a compelling reason to do so.

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