Managing aliases on the data files

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Managing aliases on the data files

Overview

Handling the aliases by programming

See also

Accessing HFSQL files via SAMBA on Linux

Accessing the databases: summary

Analysis shared between earlier WINDEV applications and WINDEV 24 applications

Assisted management of HFSQL errors

Automatic data file modification: new date format

Automatic modification of data files

Browsing the HFSQL data files

Communication by GPRS

Connecting to a database via RPC

Errors while managing data files

Filtering a data file, a view or a query

HFSQL data files exceeding 2 gigabytes

HFSQL in network mode on a server running Windows NT4, 2000, XP or 2003

HFSQL management functions

HFSQL management functions (prefix syntax)

HFSQL thumbnails

HFSQL: Change of name

Hyper File functions available for backward compatibility

Locking data files: correspondence between WINDEV 5.5 and the later versions

Management errors specific to Native Accesses

Managing NULL in HFSQL

Managing aliases on the data files

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Managing space characters in the searches?

Managing the Unicode format in the HFSQL files

Managing the automatic identifiers when adding a record

Modifying the query content

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SQL functions: Special case

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The .REP file

The HFSQL views

The composite keys

The different types of browse available in SQL

Unalterable data files

WDModFic : Tool for automatic modification of data files

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Overview
Several physical data files with an identical logical description
Several logical data files linked to a single physical data file
Handling the aliases by programming
The WLanguage functions
Create an alias on what?
Characteristics of an alias
Handling the alias file and its items

WINDEV

WEBDEV

WINDEV Mobile

Others

See also

HFSQL management functions

Managing aliases on the data files

Available only with these kinds of connection

Overview

The aliases are used to handle:

Several physical data files with the same description in the analysis
Several logical data files described in the analysis that handle the same physical data file.

Versions 17 and later

This feature is now available for iPhone/iPad applications.

New in version 17

This feature is now available for iPhone/iPad applications.

Remark: From version 19, HFSQL is the new name of HyperFileSQL.

Several physical data files with an identical logical description

For example: You have the ability to manage at the same time:

The Customer2000.fic file that contains the backup of the customers for the year 2000
The Customer.fic file that contains the customer references for the current year

These two data files have the same logical description in the analysis: the CUSTOMER file. By default, the description of CUSTOMER file found in the analysis is linked to the Customer.fic file.

To use the Customer2000.Fic data file, you must "copy" the description of the CUSTOMER data file found in the analysis: to do so, create an alias with HAlias. The corresponding code line is as follows:

HAlias(Customer, Customer2000)

The two files will be handled the same way with the HFSQL functions.

Several logical data files linked to a single physical data file

You have the ability to perform several parallel searches on the same physical data file or a search and a filter in parallel on the data file.

Example: The Customer.Fic data file is associated with the logical file named Customer in the analysis. To filter the records found in the Customer.fic data file and to browse at the same time all the records found in this data file, you must:

"Copy" the description of the CUSTOMER data file into the analysis: to do so, create an alias with HAlias.
Associate the description of the alias with the physical data file named Customer.Fic (HChangeName).

Remark: This method is used to manage several HFSQL contexts for the same physical data file.

Handling the aliases by programming

The WLanguage functions

Several functions are used to handle the aliases:


Versions 09 and later HAlias New in version 09 HAlias HAlias	Creates a logical alias of a data file (or query) or cancels all existing aliases.
Versions 09 and later HCancelAlias New in version 09 HCancelAlias HCancelAlias	Cancels an alias that was declared beforehand by HAlias.

Other functions can intervene in the definition and use of aliases:


Versions 09 and later HChangeDir New in version 09 HChangeDir HChangeDir	Modifies the access path to a data file (which means the directory where the file will be used).
Versions 09 and later HChangeName New in version 09 HChangeName HChangeName	Modifies the physical name of a data file.

Create an alias on what?

You have the ability to create and handle aliases for the following elements:

Data file described in the analysis
Data file described dynamically
Query created in the query editor
HFSQL Classic view
Alias

Characteristics of an alias

Physical data file associated with an alias:
By default, the name specified for the alias is assigned to the physical data file corresponding to the alias. To associate the alias with a physical data file of different name, you must use HChangeName and HChangeDir.
Password of an alias:
By default, the password of an alias file is identical to the password of the source data file. This password can be modified by HPass. The name of the data file used in this function corresponds to the name of the alias.
Re-indexing:
The alias files can be re-indexed.
Automatic modification of the data files:
This operation can be applied to the alias files.

Handling the alias file and its items

Code editor: To avoid the "Unknown identifier" error when using an alias file and its items, we recommend that you use a data source to declare the name of the alias before using HAlias.
For example:

Orders2000 is Data Source
HAlias(Orders, Orders2000)

Caution: the Extern keyword can be used but it slows down the execution significantly.
Window editor or page editor: the controls and the tables cannot be directly associated with the items found in the alias files. The controls must be assigned one by one by programming.
Remark: to redefine the field relationships by programming, it is possible to use either the ControlAlias function or the Property FileLink.