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Delphi: Cómo insertar ficheros en un campo de una tabla MySQL con Delphi
Bases de Datos


Este artículo explica cómo insertar ficheros de cualquier tipo en un campo de una tabla de MySQL, utilizando Delphi como lenguaje de programación. Os explicamos como añadir un fichero y cómo sacarlo/guardarlo una vez insertado.



Insertar ficheros (imágenes, pdf, etc) en una tabla MySQL

INSERTAR FICHEROS EN TABLAS MYSQL CON DELPHI

Este artículo explica paso a paso, con capturas de pantalla, cómo insertar ficheros de cualquier tipo en un campo de una tabla de MySQL, utilizando Delphi como lenguaje de programación. Os explicamos como añadir un fichero y cómo sacarlo/guardarlo una vez insertado. Os explicamos con un ejemplo cómo hacer un mini gestor documental, una aplicación donde almacenar ficheros, con su descripción correspondiente, para poder tenerlos alojados en un lugar común.

En primer lugar nos crearemos la tabla en MySQL, para ello podremos utilizar cualquier aplicación que permita acceder a MySQL y ejecutar consultas SQL de creación de tablas. En nuestro caso utilizaremos "AjpdSoft Administración Bases de Datos", disponible gratuitamente en esta web, este es el enlace de la descarga (es necesario ser usuario registrado):

Descargar AjpdSoft Administración Bases de datos

Con esta aplicación o con cualquier otra que admita acceso a MySQL crearemos la tabla donde alojaremos los ficheros, la sentencia SQL para crear la tabla sería la siguiente:

CREATE TABLE documentos (
  codigo int(10) unsigned NOT NULL auto_increment,
  ficherodescripcion varchar(255) default NULL,
  ficherorutafisica varchar(255) default NULL,

  ficherocontenido longblob,

  fechaalta datetime default NULL,
  observacion text default NULL,
  PRIMARY KEY (codigo)
)

el campo donde se alojará el fichero será "ficherocontenido" de tipo longblob (admite hasta ficheros de 4 GB, aunque no recomendamos superar 1 MB si la base de datos va a ser accesible desde Internet) . A continuación os mostramos captura de pantalla de la aplicación en el proceso de creación de la tabla:

Tras crear la tabla abriremos Delphi para realizar la aplicación que gestione la tabla creada anteriormente. Desde Delphi, pulsaremos "File" - "New application". En nuestro caso, para el acceso a MySQL utilizaremos un componente gratuito para Delphi y MySQL llamado ZeosDBO, disponible en http://sourceforge.net/projects/zeoslib, en el siguiente enlace (de esta web) os explicamos cómo instalarlo paso a paso:

Instalar ZeosDBO para Delphi

En nuestra aplicación de Delphi añadiremos los siguientes componentes al formulario principal:

  • ZConnection: componente para la conexión con el servidor de base de datos MySQL.
  • ZTable: componente para manipulación de tablas MySQL.
  • DataSource: componente que enlaza el ZTable con los cuadros de edición de los campos de la tabla MySQL.
  • DBNavitagor: componente visual con los botones típicos para manipular registros (editar, validar, eliminar, insertar, refrescar, siguiente, anterior, primero, último).

Os indicamos las propiedades que hay que cambiar en los diferentes componentes:

  • En la propiedad "DataSet" del componente "DataSource" pondremos el nombre del componente "ZTable", de esta forma quedarán enlazados.
  • En la propiedad "DataSource" del componente DBNavigator pondremos el nombre del componente "DataSource", de esta forma quedará enlazado el DBNavigator con el ZTable pues , éste a su vez, está enlazado con el DataSource.
  • En la propiedad "Connection" del componente "ZTable" pondremos el nombre del componente "ZConnection".

Para ver todas las propiedades y los componentes restantes (formulario, botones, savedialog, opendialog, etc), os recomendamos que descargéis el código fuente de la aplicación, pulsando aquí.

El formulario de Delphi quedará de la siguiente forma:

Para realizar la conexión con la base de datos MySQL utilizaremos el siguiente código:

procedure TformMenuPrincipal.FormCreate(Sender: TObject);
begin
  dbConexion.Disconnect;
  dbConexion.HostName := leCadINI('BD','Servidor','localhost');
  dbConexion.Port := strtoint(leCadINI('BD','Puerto','3306'));
  dbConexion.Catalog := leCadINI('BD','Catálogo','gestordocumental');
  dbConexion.Database := leCadINI('BD','Catálogo','gestordocumental');
  dbConexion.User := leCadINI('BD','Usuario','root');
  dbConexion.Password := leCadINI('BD','Contraseña','');
  dbConexion.Connect;
  tTabla.Active := true;
end;

Donde utilizamos la función "leeCadINI" para leer valore fichero ini, con el siguiente código:

//Lee una cadena de texto de un INI
function leCadINI (clave, cadena : string; defecto : string) : string;
begin
  with tinifile.create (changefileext(paramstr(0),'.INI')) do
  try
    result := readString (clave, cadena, defecto);
  finally
    free;
  end;
end;

El procedimiento que utilizaremos para insertar un fichero al registro actual será:

procedure TformMenuPrincipal.bInsertarFicheroClick(Sender: TObject);
begin
  if not (tTabla.State in [dsedit, dsinsert]) then
    tTabla.Edit;
  if dlAbrir.Execute then
  begin
    tTablaficherocontenido.LoadFromFile(dlAbrir.FileName);
    tTablaficherorutafisica.AsString := dlAbrir.FileName;
  end;
end;

El procedimiento que utilizaremos para eliminar un fichero ya insertado será:

procedure TformMenuPrincipal.bEliminarFicheroClick(Sender: TObject);
begin
  if not (tTabla.State in [dsedit, dsinsert]) then
    tTabla.Edit;
  tTablaficherocontenido.Clear;
  tTablaficherorutafisica.AsString := '';
end;
El procedimiento que utilizaremos para descargar un fichero ya insertado en la base de datos será:
procedure TformMenuPrincipal.bDescargarFicheroClick(Sender: TObject);
begin
  if tTablaficherocontenido.AsString <> '' then
  begin
    dlGuardar.FileName := ExtractFileName(tTablaficherorutafisica.AsString);
    if dlGuardar.Execute then
      tTablaficherocontenido.SaveToFile(dlGuardar.FileName);
  end
  else
    MessageDlg('Este registro no tiene fichero asignado.', mtInformation, [mbok], 0);
end;

 

La aplicación en ejecución quedará de la siguiente forma:

Si pulsamos el botón "Añadir fichero" nos mostrará una ventana com este:

 

 

Nota: MySQL regula el tamaño máximo del fichero insertado por medio del parámetro: max_allowed_packet, no permitirá ficheros de mayor tamaño que el especificado en este parámetro. Se guarda en el fichero my.ini, en la carpeta de instalación del Servidor de MySQL, normalmente en:

C:/Archivos de programa/MySQL/MySQL Server 4.1

 Un ejemplo de contenido del fichero my.ini:

# MySQL Server Instance Configuration File
# ----------------------------------------------------------------------
# Generated by the MySQL Server Instance Configuration Wizard
#
#
# Installation Instructions
# ----------------------------------------------------------------------
#
# On Linux you can copy this file to /etc/my.cnf to set global options,
# mysql-data-dir/my.cnf to set server-specific options
# (@localstatedir@ for this installation) or to
# ~/.my.cnf to set user-specific options.
#
# On Windows you should keep this file in the installation directory
# of your server (e.g. C:/Program Files/MySQL/MySQL Server X.Y). To
# make sure the server reads the config file use the startup option
# "--defaults-file".
#
# To run run the server from the command line, execute this in a
# command line shell, e.g.
# mysqld --defaults-file="C:/Program Files/MySQL/MySQL Server X.Y/my.ini"
#
# To install the server as a Windows service manually, execute this in a
# command line shell, e.g.
# mysqld --install MySQLXY --defaults-file="C:/Program Files/MySQL/MySQL Server X.Y/my.ini"
#
# And then execute this in a command line shell to start the server, e.g.
# net start MySQLXY
#
#
# Guildlines for editing this file
# ----------------------------------------------------------------------
#
# In this file, you can use all long options that the program supports.
# If you want to know the options a program supports, start the program
# with the "--help" option.
#
# More detailed information about the individual options can also be
# found in the manual.
#
#
# CLIENT SECTION
# ----------------------------------------------------------------------
#
# The following options will be read by MySQL client applications.
# Note that only client applications shipped by MySQL are guaranteed
# to read this section. If you want your own MySQL client program to
# honor these values, you need to specify it as an option during the
# MySQL client library initialization.
#
[client]

port=3306

[mysql]

default-character-set=latin1

# SERVER SECTION
# ----------------------------------------------------------------------
#
# The following options will be read by the MySQL Server. Make sure that
# you have installed the server correctly (see above) so it reads this
# file.
#
[mysqld]

# The TCP/IP Port the MySQL Server will listen on
port=3306

#Path to installation directory. All paths are usually resolved relative to this.
basedir="C:/Archivos de programa/MySQL/MySQL Server 4.1/"

#Path to the database root
datadir=D:/MySQL

# The default character set that will be used when a new schema or table is
# created and no character set is defined
default-character-set=latin1

# The default storage engine that will be used when create new tables when
default-storage-engine=INNODB

# The maximum amount of concurrent sessions the MySQL server will
# allow. One of these connections will be reserved for a user with
# SUPER privileges to allow the administrator to login even if the
# connection limit has been reached.
max_connections=100

# Query cache is used to cache SELECT results and later return them
# without actual executing the same query once again. Having the query
# cache enabled may result in significant speed improvements, if your
# have a lot of identical queries and rarely changing tables. See the
# "Qcache_lowmem_prunes" status variable to check if the current value
# is high enough for your load.
# Note: In case your tables change very often or if your queries are
# textually different every time, the query cache may result in a
# slowdown instead of a performance improvement.
query_cache_size=0

# The number of open tables for all threads. Increasing this value
# increases the number of file descriptors that mysqld requires.
# Therefore you have to make sure to set the amount of open files
# allowed to at least 4096 in the variable "open-files-limit" in
# section [mysqld_safe]
table_cache=256

# Maximum size for internal (in-memory) temporary tables. If a table
# grows larger than this value, it is automatically converted to disk
# based table This limitation is for a single table. There can be many
# of them.
tmp_table_size=7M

# How many threads we should keep in a cache for reuse. When a client
# disconnects, the client's threads are put in the cache if there aren't
# more than thread_cache_size threads from before. This greatly reduces
# the amount of thread creations needed if you have a lot of new
# connections. (Normally this doesn't give a notable performance
# improvement if you have a good thread implementation.)
thread_cache_size=8

#*** MyISAM Specific options

# The maximum size of the temporary file MySQL is allowed to use while
# recreating the index (during REPAIR, ALTER TABLE or LOAD DATA INFILE.
# If the file-size would be bigger than this, the index will be created
# through the key cache (which is slower).
myisam_max_sort_file_size=100G

# If the temporary file used for fast index creation would be bigger
# than using the key cache by the amount specified here, then prefer the
# key cache method. This is mainly used to force long character keys in
# large tables to use the slower key cache method to create the index.
myisam_max_extra_sort_file_size=100G

# If the temporary file used for fast index creation would be bigger
# than using the key cache by the amount specified here, then prefer the
# key cache method. This is mainly used to force long character keys in
# large tables to use the slower key cache method to create the index.
myisam_sort_buffer_size=12M

# Size of the Key Buffer, used to cache index blocks for MyISAM tables.
# Do not set it larger than 30% of your available memory, as some memory
# is also required by the OS to cache rows. Even if you're not using
# MyISAM tables, you should still set it to 8-64M as it will also be
# used for internal temporary disk tables.
key_buffer_size=8M

# Size of the buffer used for doing full table scans of MyISAM tables.
# Allocated per thread, if a full scan is needed.
read_buffer_size=64K
read_rnd_buffer_size=256K

# This buffer is allocated when MySQL needs to rebuild the index in
# REPAIR, OPTIMZE, ALTER table statements as well as in LOAD DATA INFILE
# into an empty table. It is allocated per thread so be careful with
# large settings.
sort_buffer_size=256K

#*** INNODB Specific options ***

# Use this option if you have a MySQL server with InnoDB support enabled
# but you do not plan to use it. This will save memory and disk space
# and speed up some things.
#skip-innodb

# Additional memory pool that is used by InnoDB to store metadata
# information. If InnoDB requires more memory for this purpose it will
# start to allocate it from the OS. As this is fast enough on most
# recent operating systems, you normally do not need to change this
# value. SHOW INNODB STATUS will display the current amount used.
innodb_additional_mem_pool_size=2M

# If set to 1, InnoDB will flush (fsync) the transaction logs to the
# disk at each commit, which offers full ACID behavior. If you are
# willing to compromise this safety, and you are running small
# transactions, you may set this to 0 or 2 to reduce disk I/O to the
# logs. Value 0 means that the log is only written to the log file and
# the log file flushed to disk approximately once per second. Value 2
# means the log is written to the log file at each commit, but the log
# file is only flushed to disk approximately once per second.
innodb_flush_log_at_trx_commit=1

# The size of the buffer InnoDB uses for buffering log data. As soon as
# it is full, InnoDB will have to flush it to disk. As it is flushed
# once per second anyway, it does not make sense to have it very large
# (even with long transactions).
innodb_log_buffer_size=1M

# InnoDB, unlike MyISAM, uses a buffer pool to cache both indexes and
# row data. The bigger you set this the less disk I/O is needed to
# access data in tables. On a dedicated database server you may set this
# parameter up to 80% of the machine physical memory size. Do not set it
# too large, though, because competition of the physical memory may
# cause paging in the operating system. Note that on 32bit systems you
# might be limited to 2-3.5G of user level memory per process, so do not
# set it too high.
innodb_buffer_pool_size=10M

# Size of each log file in a log group. You should set the combined size
# of log files to about 25%-100% of your buffer pool size to avoid
# unneeded buffer pool flush activity on log file overwrite. However,
# note that a larger logfile size will increase the time needed for the
# recovery process.
innodb_log_file_size=10M

# Number of threads allowed inside the InnoDB kernel. The optimal value
# depends highly on the application, hardware as well as the OS
# scheduler properties. A too high value may lead to thread thrashing.
innodb_thread_concurrency=8

max_allowed_packet=100mb


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Enviado el Domingo, 18 febrero a las 16:35:58 por ajpdsoft
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