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<div id="product_name"><big><strong>LuaSQL</strong></big></div>
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<h1>LuaSQL</h1>
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<h2><a name="introduction"></a>Introduction</h2>
<p>LuaSQL is a simple interface from Lua to a number of database management systems.
It includes a set of drivers to some popular databases
(currently PostgreSQL, ODBC, MySQL, SQLite, Oracle, and ADO;
Interbase and Sybase are in our plans).
LuaSQL defines a simple object-oriented API.
All drivers should implement this common API,
but each one is free to offer extensions.</p>
<p>LuaSQL defines one single global variable,
a table called <code>luasql</code>.
This table is used to store the initialization methods of the
loaded drivers.
These methods are used to create an
<a href="#environment_object">environment object</a>
which is used to create a
<a href="#connection_object">connection object</a>.
A connection object can execute SQL statements and eventually
create a
<a href="#cursor_object">cursor object</a>
which is used to retrieve data.
</p>
<p>
LuaSQL is free software and uses the same
<a href="license.html">license</a>
as Lua 5.1.
</p>
<h2><a name="compiling"></a>Compiling</h2>
<p>LuaSQL is distributed as a set of C source files:
a pair of common source and header files (<code>luasql.h</code> and <code>luasql.c</code>);
and one source file for each driver.
Each driver should be compiled with the luasql.c file to generate a library.
This library can be linked to the application or dynamically loaded.
The initialization function is <code>luaopen_luasql<em>drivername</em></code> and it is a Lua
<a href="http://www.lua.org/manual/5.1/manual.html#pdf-require"><code>open-library</code></a> compatible function.
</p>
<h2><a name="installation"></a>Installation</h2>
<p>All LuaSQL drivers follow the
<a href="http://www.keplerproject.org/compat">package model</a>
for Lua 5.1 and therefore should be "installed" in your
<code>package.path</code>.</p>
<p>Windows users can use the compiled versions of LuaSQL available at
<a href="http://luaforge.net/projects/luasql/files">LuaForge</a></p>
<p>In order to use LuaSQL with ADO, make sure that you have
<a href="http://www.tecgraf.puc-rio.br/~rcerq/luacom">LuaCOM 1.3</a>
for Lua 5.1 installed.</p>
<h2><a name="errors"></a>Error handling</h2>
<p>
LuaSQL is just an abstraction layer that communicates between Lua
and a database system.
Therefore errors can occur on both levels, that is,
inside the database client or inside LuaSQL driver.
</p>
<p>
Errors such as malformed SQL statements, unknown table names etc.
are called <em>database errors</em> and
will be reported by the function/method returning <code>nil</code> followed
by the error message provided by the database system.
Errors such as wrong parameters, absent connection, invalid objects etc.,
called <em>API errors</em>,
are usually program errors and so will raise a Lua error.
</p>
<p>
This behavior will be followed by all functions/methods
described in this document unless otherwise stated.
</p>
<h2><a name="drivers"></a>Drivers</h2>
<p>
A LuaSQL driver allows the use of the LuaSQL API with a database management system
that corresponds to the driver. To use a driver you have to load it in the
<code>luasql</code> table. The example below
</p>
<pre class="example">
require "luasql.odbc"
</pre>
<p>
loads the ODBC driver in the <code>luasql</code> table. Note that you can have more than one
driver loaded at the same time doing something like:
</p>
<pre class="example">
require "luasql.odbc"
require "luasql.oci8"
</pre>
<p>
This example also shows that the driver name not always correspond to the
Database name, but to the driver name in the file system. Since it refers to
the OCI8 API, the Oracle driver has the name <code>oci8</code> instead of
<code>oracle</code>.
</p>
<p>
Some drivers, such as the MySQL, have libraries for a number of database versions that
use the same file name (<code>mysql</code>). In this case it is not possible to
load more than one version of the MySQL driver in the <code>luasql</code> table.
</p>
<h2><a name="environment_object"></a>Environment Objects</h2>
<p>An environment object is created by calling the driver's initialization
function that is stored in the <code>luasql</code> table, indexed with the same
name as the driver (odbc, postgres etc). For example,
</p>
<pre class="example">
env = luasql.odbc()
</pre>
<p>will try to create an environment object using the ODBC driver.</p>
<h4>Methods</h4>
<dl class="reference">
<dt><a name="env_close"></a><strong><code>env:close()</code></strong></dt>
<dd>Closes the environment <code>env</code>.
Only successful if all connections pertaining to it were closed first.<br/>
Returns: <code>true</code> in case of success; <code>false</code> when
the object is already closed.</dd>
<dt><a name="env_connect"></a><strong><code>env:connect(sourcename[,username[,password]])</code></strong></dt>
<dd>Connects to a data source specified in <code>sourcename</code> using
<code>username</code> and <code>password</code> if they are supplied.<br/>
The <code>sourcename</code> may vary according to each driver.
Some use a simple database name, like PostgreSQL, MySQL and SQLite;
the ODBC driver expects the name of the DSN;
the Oracle driver expects the service name;
See also: <a href="#postgres_extensions">PostgreSQL</a>,
and <a href="#mysql_extensions">MySQL</a> extensions.<br/>
Returns: a <a href="#connection_object">connection object</a>.</dd>
</dl>
<h2><a name="connection_object"></a>Connection Objects</h2>
<p>A connection object contains specific attributes and parameters of a
single data source connection.
A connection object is created by calling the
<code><a href="#env_connect">environment:connect</a></code>
method.</p>
<h4>Methods</h4>
<dl class="reference">
<dt><a name="conn_close"></a><strong><code>conn:close()</code></strong></dt>
<dd>Closes the connection <code>conn</code>.
Only successful if all cursors pertaining to it have been closed and the connection is still open.<br/>
Returns: <code>true</code> in case of success and <code>false</code> in case of failure.</dd>
<dt><a name="conn_commit"></a><strong><code>conn:commit()</code></strong></dt>
<dd>Commits the current transaction.
This feature might not work on database systems that do not implement
transactions.<br/>
Returns: <code>true</code> in case of success and <code>false</code> when
the operation could not be performed or when it is not implemented.</dd>
<dt><a name="conn_execute"></a><strong><code>conn:execute(statement)</code></strong></dt>
<dd>Executes the given SQL <code>statement</code>.<br/>
Returns: a <a href="#cursor_object">cursor object</a>
if there are results, or the number of rows affected by the command otherwise.</dd>
<dt><a name="conn_rollback"></a><strong><code>conn:rollback()</code></strong></dt>
<dd>Rolls back the current transaction.
This feature might not work on database systems that do not implement
transactions.<br/>
Returns: <code>true</code> in case of success and <code>false</code> when
the operation could not be performed or when it is not implemented.</dd>
<dt><a name="conn_setautocommit"></a><strong><code>conn:setautocommit(boolean)</code></strong></dt>
<dd>Turns on or off the "auto commit" mode.
This feature might not work on database systems that do not implement
transactions.
On database systems that do not have the concept of "auto commit mode",
but do implement transactions, this mechanism is implemented by the driver.
<br/>
Returns: <code>true</code> in case of success and <code>false</code> when
the operation could not be performed or when it is not implemented.</dd>
</dl>
<h2><a name="cursor_object"></a>Cursor Objects</h2>
<p>A cursor object contains methods to retrieve data resulting from an
executed statement. A cursor object is created by using the
<code><a href="#conn_execute">connection:execute</a></code>
function.
See also <a href="#postgres_extensions">PostgreSQL</a>
and <a href="#oracle_extensions">Oracle</a> extensions.</p>
<h4>Methods</h4>
<dl class="reference">
<dt><a name="cur_close"></a><strong><code>cur:close()</code></strong></dt>
<dd>Closes this cursor.<br/>
Returns: <code>true</code> in case of success and <code>false</code> when
the object is already closed.</dd>
<dt><a name="cur_fetch"></a><strong><code>cur:fetch([table[,modestring]])</code></strong></dt>
<dd>Retrieves the next row of results.<br/>
If <code>fetch</code> is called without parameters,
the results will be returned directly to the caller.
If <code>fetch</code> is called with a table, the results will be copied
into the table and the changed table will be returned.
In this case, an optional <code>modestring</code> parameter can be used.
It is just a string indicating how the resulting table should be constructed.
The mode string can contain:
<dl>
<dt><strong>"n"</strong></dt><dd>the resulting table will have numerical indices (default)</dd>
<dt><strong>"a"</strong></dt><dd>the resulting table will have alphanumerical indices</dd>
</dl>
<br/>
The <em>numerical indices</em> are the positions of the fields in the SELECT
statement;
the <em>alphanumerical indices</em> are the names of the fields.<br/>
The optional <code>table</code> parameter is a table that should be
used to store the next row.
This allows the use of a unique table for many fetches, which
can improve the overall performance.<br/>
There is no guarantee about the types of the results: they may or may not be converted to adequate Lua types by the driver.
In the current implementation,
the PostgreSQL and MySQL drivers return all values as strings
while the ODBC and Oracle drivers convert them to Lua types.<br/>
Returns: data, as above, or <code>nil</code> if there are no more rows.
Note that this method could return <code>nil</code> as a valid result.</dd>
<dt><a name="cur_colnames"></a><strong><code>cur:getcolnames()</code></strong></dt>
<dd>Returns: a list (table) of column names.</dd>
<dt><a name="cur_coltypes"></a><strong><code>cur:getcoltypes()</code></strong></dt>
<dd>Returns: a list (table) of column types.</dd>
</dl>
<p><a name="extensions"></a></p>
<h2><a name="postgres_extensions"></a>PostgreSQL Extensions</h2>
<p>Besides the basic functionality provided by all drivers,
the Postgres driver also offers these extra features:</p>
<dl class="reference">
<dt><strong><code>env:connect(sourcename[,username[,password[,hostname[,port]]]])</code></strong></dt>
<dd>In the PostgreSQL driver, this method adds two optional parameters
that indicate the hostname and port to connect.
Also, the first parameter can contain all connection information,
as stated in the documentation for <code>PQconnectdb</code> function
in the PostgreSQL manual
(e.g. <small><code>environment:connect("dbname=<<em>name</em>> user=<<em>username</em>>")</code></small>) <br/>
See also: <a href="#environment_object">environment objects</a><br/>
Returns: a <a href="#connection_object">connection object</a></dd>
<dt><strong><code>cur:numrows()</code></strong></dt>
<dd>See also: <a href="#cursor_object">cursor objects</a><br/>
Returns: the number of rows in the query result.</dd>
</dl>
<h2><a name="mysql_extensions"></a>MySQL Extensions</h2>
<p>Besides the basic functionality provided by all drivers,
the MySQL driver also offers these extra features:</p>
<dl class="reference">
<dt><strong><code>env:connect(sourcename[,username[,password[,hostname[,port]]]])</code></strong></dt>
<dd>In the MySQL driver, this method adds two optional parameters
that indicate the hostname and port to connect.
See also: <a href="#environment_object">environment objects</a><br/>
Returns: a <a href="#connection_object">connection object</a></dd>
<dt><strong><code>cur:numrows()</code></strong></dt>
<dd>See also: <a href="#cursor_object">cursor objects</a><br/>
Returns: the number of rows in the query result.</dd>
</dl>
<p>Notes:</p>
<p>This driver is compatible with versions 4.0, 4.1 and 5.0 of the
MySQL API. Only from version 4.1 MySQL provides support for transactions by using
BDB or INNODB tables.
Therefore, with version 4.0 or without one of these types of tables, the
methods <code>commit</code>, <code>rollback</code> and
<code>setautocommit</code> will not work.</p>
<p>If you are using LuaSQL 2.0, <strong><code>cur:numrows()</code></strong>
is available only in version 2.0.2 or later.</p>
<h2><a name="oracle_extensions"></a>Oracle Extensions</h2>
<p>Besides the basic functionality provided by all drivers,
the Oracle driver also offers this extra feature:</p>
<dl class="reference">
<dt><strong><code>cur:numrows()</code></strong></dt>
<dd>See also: <a href="#cursor_object">cursor objects</a><br/>
Returns: the number of rows in the query result.</dd>
</dl>
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