File Description (Type of variable)

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Managing databases

HFSQL functions

Types of HFSQL variables

File Description

Presentation

Example

Properties specific to the description of data files

How to describe data files programmatically?

Handling the items of a data file described programmatically

Logging

See also

File Description (Type of variable)

In french: Description de Fichier (Type de variable)

Available only with these kinds of connection

The File Description variable is used to programmatically describe data files. The description of each data file is validated by HDescribeFile.

After this validation:

This data file can be handled like any other data file described in the analysis.
The "File Description" variable is reinitialized and can be used to describe another data file.

Example

AFile is File Description
MyFile1, MyFile2 are File Descriptions

// Describe the "CUSTOMER" data file
AFile is File Description

AFile.Name = "CUSTOMER"
AFile.Type = hFileNormal
AFile.FicEncryption = hEncryptionStandard

// Description of the data file items
...

// Validate the description of "CUSTOMER"
HDescribeFile(AFile)

Syntax

Declaring one or more descriptions of data files Hide the details

<Variable name> is File Description
<Variable name 1>, <Variable name 2> are File Descriptions

<Variable name>:

Name of the "File Description" variable to declare.
Remark: The a and an keywords are optional: they provide better readability.

Describing a "File Description" variable Hide the details

To describe a "File Description" variable:

Use the WLanguage properties specific to the descriptions of data files. For more details, see remarks.

To validate the description of a "File Description" variable:

Use the HDescribeFile function.

Remarks

Properties specific to the description of data files

The table below presents the properties specific to the description of data files:

Remark: The properties in bold followed by a star (*) must necessarily be initialized when a data file is described through programming.

Property name	Effect

MmoPackMethod	Compression mode of the MMO file (containing the text and binary memos) associated with the data file
FicEncryption	Data file encryption mode
MmoEncryption	Encryption mode of memo file (.MMO extension) associated with the data file
NdxEncryption	Encryption mode of index file associated with the data file
CtAccess	Type of access to the file when connecting to a specific table via OLE DB (taking into account the changes made with HConnect)
CtDescribedAccess	Type of access to the file when connecting to a specific table via OLE DB (ignoring the changes made with HConnect)
CtDatabase	OLE DB data source when connecting to a specific table (taking into account the changes made with HConnect)
CtDescribedDatabase	OLE DB data source when connecting to a specific table (ignoring the changes made with HConnect)
CtDescribedCaption	Caption of the connection to the OLE DB data source
CtDescribedPassword	Password used to open the file during an OLE DB connection
CtOLEDBProvider	Name of the OLE DB server used (taking into account the changes made with HConnect).
CtDescribedOLEDBProvider	Name of the OLE DB server (ignoring the changes made with HConnect).
CtUserName	Name of the user during an OLE DB connection (taking into account the changes made by HConnect).
CtDescribedUserName	Name of the user during an OLE DB connection (ignoring the changes made with HConnect).
Format	Format of data in the data file (ANSI or Unicode).
HugeFile	Maximum size of a data file.
Unalterable	Unalterability of data files.
LogMethod	Log mode of a data file.
WDD55Password	Password that will be used to handle a file defined through programming in Hyper File 5.5 format in an analysis in WINDEV format.
Name ( * )	Name of HFSQL file.
Name55	Logical name of a file in Hyper File 5.5 format found in an analysis in WINDEV format.
DescribedName	Logical name of a data file.
PhysicalName	Physical name of data files.
DescribedPhysicalName	Physical name of HFSQL files (while ignoring the changes of name performed by HChangeName).
New in version 28 NullableIndex	Support of NULL values in key items.
NullSupported	Support of NULL values.
RepeatableReadSupported	The file is used in an HFSQL Client/Server transaction that includes a "Repeatable Read" isolation mode.
Directory	Physical directory of HFSQL files (this property takes into account the changes of directory performed by HChangeDir or HSubstDir).
DescribedDirectory	Physical directory of HFSQL files (this property ignores the changes of directory performed by HChangeDir or HSubstDir).
LogDirectory	Directory of log file described in the analysis.
TextItemCompleted	Fills (or not) the text items with space characters.
Secure	Security level regarding the encryption of data files.
Type	Type of data file.
WDD55	Path of the WDD file in 5.5 format used to handle the data files in 5.5 format in a WINDEV application.

How to describe data files programmatically?

To describe data files programmatically:

Declare the "File Description", "Item Description", "FullTextIndex Description" and "Link description" variables (if necessary).
For each data file:
- Describe the characteristics of the data file using HFSQL properties.
- Describe the characteristics of the items using HFSQL properties.
- Validate the description of each item (HDescribeItem).
- If necessary, describe the characteristics of full-text indexes using HFSQL properties.
- Validate the description of each full-text index (HDescribeFullTextIndex).
- Validate the data file description (HDescribeFile).
If necessary, describe the characteristics of the links using HFSQL properties.
If necessary, validate the description of each link (HDescribeLink).

Handling the items of a data file described programmatically

When creating a data file in the data model editor, the names of the data files and items are automatically recognized by the compiler.

When creating a data file using a "File Description" variable, the names of the data file and its items can be defined with the Name property. These names are not automatically recognized by the compiler. A compilation error occurs if these names are used to identify the data file or the items.

The name of the data file must be declared as data source using the data source keyword, for the compiler to recognize this name. This data file can be handled by its name in the code editor.

For example:

AFile is File Description
...
AFile.Name = "CUSTOMER"
...
HDescribeFile("CUSTOMER")
...
CUSTOMER is Data Source
...
HReadFirst(CUSTOMER, "CUSTNAME")

Remark: The name of the data file can also be declared with the Extern keyword. However, the process execution will be slower.

Logging

When the data file is described programmatically:

if the data file is logged and if no item is logged, all the items (except for the composite keys) are automatically logged.
if the data file is logged and if at least one item is logged, the other items are not modified.