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File: newdbsupportimplementationguide.html
Role: Documentation
Content type: text/plain
Description: Support for other DBs implementation guide
Class: PersistClass
DB access wrapper & storing objects in DB tables
Author: By
Last change: added comment on query implementation
Date: 8 years ago
Size: 2,611 bytes


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<head><title>DB Connection implementation guide</title></head>
<p>This guide describes how you can add support to other databases to DbConnection / PersistClass. To see an existing implementation, check DbConnectionMysql.php</p>
<h1>The abstract DbConnection class</h1>
Objects of this class are responsible for holding and managing a database connection and the resultset of the last executed query. It provides an abstraction layer that allows any database system to be used in the same way.
The base class defines the following attributes:
<li><b>$link</b>: Database link</li>
<li><b>$result</b>: ResultSet object (containing the results of the previous query)</li>
<li><b>$numRows</b>: Containing the number of returned rows or the number of updated/deleted rows of the previous query</li>
This class declares the following methods that will need to be implemented:
<li><b>query($q)</b>: Executes an SQL query.</li>
<li><b>next()</b>: returns next row from the resultset as an associative array</li>
<li><b>getLastId()</b>: returns the ID of the last inserted row</li>
<li><b>closeConnection()</b>: closes database connection</li>
<li><b>getLastId()</b>: returns the primary key of the last inserted row</li>
<li><b>cloneConnection()</b>: creates a new DbConnection object by reusing the existing database connection</li>
<li><b>escape($string, $quoted = true)</b>: escapes a string value and wraps them into quotes (optional)</li>
<li><b>startTransaction()</b>: starts transaction</li>
<li><b>commit()</b>: commits transaction</li>
<li><b>rollBack()</b>: rolls back transaction</li>
<h2>Construction & connection</h2>
The object has to be responsible for opening a database connection. Throws ConnectionException if it fails to do so. The DbConnectionMysql does that with its connect() method. (not in constructor, makes "cloning" easier in cloneConnection)
<h2>Additional method implementation requirements</h2>
<li><b>query($q)</b>: Executes an SQL query. Puts number of affected rows into numRows and returns it. Throws ConnectionException if there is a connection error, throws QueryException in case of an SQL query error.</li>
<li><b>next()</b>: Returns next row from the recordset as an associative array. Returns null if there are no more rows.</li>
<li><b>getLastId()</b>: Optional. Only implement for databases that support auto-increment</li>