TPSQL/es

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TPSQL e un paquete modificado bajo LGPL para Lazarus. Define dos componentes, TPSQLDatabase y TPSQLDataset, permitiendo a las aplicaciones conectar con servidores de bases de datos PostgreSQL en redes que utilizan TCP/IP.

La descarga contiene los ficheros de componentes Pascal, el fichero de paquete para Lazarus y los ficheros de recursos junto con los ficheros de texto que describen la licencia modified-LGPL.

Este componente fué diseñado para su utilización en aplicaciones corriendo bajo plataformas Linux y Win32.

Autor

Antonio d'Avino

Licencia

LGPL modificada (leer COPYING.modifiedLGPL y COPYING.LGPL que se incluyen en el paquete).

Descarga

La última versión estable se puede encontrar en Lazarus CCR Files page o en la página web del autor http://infoconsult.homelinux.net.

Historial de cambios

• Version 0.4.0 2005/06/01
• Version 0.4.1 2005/06/02

 - ClientEncoding property added to TPSQLDatabase class. 

• Version 0.4.2 2005/06/03

 - Some changes to destroy method of TPSQLDatabase/TPSQLDataset for avoiding exception
   when closing IDE/project with components in Active/Connected status.
 - Base path in archived files changed from 'usr/share/lazarus/components/psql' to 'psql'

• Version 0.4.6 2005/06/06

 - Executing queries that doesn't return data column now raises an exception.
 - commandQuery function added (see Usage section).
 - beginTransaction/commitTransaction/rollbackTransaction support added (see Usage section).
 - More ClientEncoding entities added.

Dependencias / Requerimientos del sistema

• Lazarus 0.9.6 (FPC 1.9.8)

Stado: estable

Issues: Testeado bajo Windows (Win2K) y Linux (Mdk 10.1). Servidor de base de datos: PostgreSQL 8.0.3 (corriendo en ambas plataformas).

Instalación

• In the lazarus/components directory, untar (unzip) the files from psql-laz-package-<version>.tar.gz file. The psql folder will be created.
• Open lazarus
• Open the package psql_laz.lpk with Component/Open package file (.lpk)
• (Click on Compile only if you don't want to install the component into the IDE)
• Click on Install and answer 'Yes' when you are asked about Lazarus rebuilding. A new tab named 'PSQL' will be created in the components palette.

Nota importante para los usuarios de Win32.

En caso de experimentar dificultades a la hora de compilar los ficheros Pascal del paquete, puede que se necesite añadir  la siguiente trayectoria:

 
<some-drive>:<some-path>\lazarus\lcl\units\i386-win32 
(ie: c:\programs\lazarus\lcl\units\i386-win32)
 
to the 'Other unit files ...' in 'Paths' tab of 'Compiler Options' of the lazarus package manager   
window.

Usage

Drop a TPSQLDatabase component on a form, for any different PostgreSQL database your application needs to connect to. Mandatory property of this component you have to set are:

• DatabaseName : The name of the PostgreSQL database that your application needs to connect to.
• HostName : the IP address or the URL of the PC hosting the PostgreSQL server.
• UserName : The name of an user having permission to access to host/database.

Optionally you may need to set Password property for correct connection to server. Then, to activate the connection, you neet to set the Connected property to 'True'. An exception will be raised if connection failed (wrong parameters, user with no permission to access the host/database, network errors or PostgreSQL server not active). Set this property to 'False' for closing connection.

- Note about the ClientEncoding property.

The ClientEncoding property allows user to set a character set for the client
application different from the one defined for the database. The PostgreSQL server
make a 'translation' between the two sets.  However a "ClientEncoding change failed" 
exception may be the result of a ClientEncoding property change. This may be due to
a database character set incompatible with the clientencoding you selected. IE,  
the char set 'LATIN9' is not compatible with a  'WIN1250'. You select the default
char set for the whole database cluster when you create it with the command
'initdb', using the -E option:  IE.   'initdb -E UNICODE'.  Also, you can define a
different character set for any database you create (different from the 
default one of the whole db cluster),  also with the  -E option:

IE. 'createdb  -E UNICODE Test' 
 
                    or

CREATE DATABASE TEST WITH ENCODING 'UNICODE';

(note you must  quote the character set  name in the 'CREATE DATABASE' command).

I suggest to set UNICODE character set as the default for your db cluster (or for the
database you create), because it is compatible with the whole set of charset available
for the client, except the MULE_INTERNAL.

Now you may drop a TPSQLDataset component on the form for any table connection you need. The main property to set on this component type is the Database one. A dropdown menu allows you to select one of any TDatabase descendant component present on form (of course, you must select a TPSQLDatabase component).

You also need to provide a valid SQL statement in SQL property. Now, you are able to open the TPSQLDataset, setting to 'True' the Active property. Several exceptions are provided for signaling failing conditions. Please, refer to TDataSet documentation for infos and examples about using the TPSQLDataset component in order to access to SQL retrieved data rows as well as conneting to Data Controls components. However, procedures and functions added to parent class are explained here:

- function commandQuery ( query : String) : ShortInt.

Use this function for submit queries that doesn't returns data columns, as update queries
(ie. update, insert, delete etc.). Current dataset is not affected, however it will reflect 
changes made by execution of commandQuery itself, if it has some influence on current 
dataset.Function returns 0 if succeded, -1 if failed. No exceptions are provided.

- procedure beginTransaction

                          Starts a SQL transaction session. Changes to table may be submitted
                          using the commandQuery function.

- procedure commitTransaction

                          Ends a SQL transaction session, commiting changes submitted starting
                          from last beginTransaction execution.

- procedure rollbackTransaction

                          Ends a SQL transaction session, aborting changes.