- Characteristics of created data file
- Additional files created
- Managing passwords
- Managing fatal errors when creating a data file
- Managing non-Latin character sets
- Replication: Range of identifiers
- Priority for defining the location of log files
- Creating or opening an existing table
- Managing indexes
- Creating the data file from its description
In french: HCréationSiInexistant
Not available with this kind of connection
Performs the following operations:
- If the data file does not exist, creates an empty data file (".FIC" extension) with the index file and the memo file if necessary.
The function is equivalent to HCreation.
- If the data file exists, opens the data file.
In this case, the function is equivalent to HOpen.
To optimize the call to HCreationIfNotFound, the file can be opened only when accessing the data file for the first time (using the hDelayedOpening constant).
: The automatic creation of non-existing data files can be enabled in the project description ("Files" tab of the project description, "Automatically create the data files when they are opened"). HCreationIfNotFound
is automatically used if the data file does not exist when it is handled for the first time.
If the data file is logged, you can specify the location of the log files.
If integrity constraints have been defined and if they are supported, the links are updated by the server when creating the data file.
// Create all the data files described in the analysis
// with the "PSW" password
// Create the Orders data file (described in the analysis)
<Result> = HCreationIfNotFound([<Data file> [, <Password> [, <Path of the JNL file> [, <Path of the JournalOperation file>]]] [, <Option>]])
- True if the data file was created or opened,
- False if a problem occurs. HError is used to identify the error. If a fatal error occurs, a specific process is required to continue the program and to check whether the data file was created (see the Notes).
<Data file>: Optional character string
Name of data file to use.
If this name is not specified, HCreationIfNotFound will use the last data file used by the last HFSQL function (function starting with "H").
If this parameter is equal to "*", all the data files found in the current analysis will be created or opened. If a password is specified, this password is used for all the data files.
This parameter can also correspond to the name of a group of files (or custom-folder) defined in the analysis (not available in Android and Android widget). If a password is specified, this password is used for all the data files of the group.
Caution: this parameter cannot be a variable of type File description.
<Password>: Optional character string
- Password associated with the data file.
- Empty string ("") if no password is used.
<Path of the JNL file>: Optional character string
Access path to the JNL file associated with the logged data file. This parameter is only taken into account if the data file is logged. In this case, <File name>JNL.fic will be created at the specified location.
This parameter must not be specified. In HFSQL Client/Server, the path of JNL file is defined and it cannot be modified.
This parameter is ignored.
<Path of the JournalOperation file>: Optional character string
Access path to the JournalOperation file and to the JournalIdentification file associated with the logged data file. The JournalOperation file contains all the operations performed on the logged data file. This parameter is only taken into account if the data file is logged.
This parameter must not be specified. In HFSQL Client/Server, the path of operation file is defined and it cannot be modified.
This parameter is ignored.
<Option>: Optional constant
Optimize the opening of existing data files.
|hChangeCharset||The character set defined by ChangeCharset will be taken into account in the new data file. Sorts, searches, ... on string keys (strings, characters, date and time) will be performed according to this character set.|
|hDelayedOpening||If the data file already exists, it will be opened during the first access to the data file. If the data file does not exist, it is created and opened.|
|hNoLink||Management of integrity: The links are not updated on the server (creation, modification or deletion).|
Reminder: By default, the links are updated on the server when creating a data file.
This constant is available in HFSQL Client/Server mode only.
This parameter is ignored.
Characteristics of created data file
The characteristics of created data file are as follows:
- Name of the data file:
Physical name defined during the file description in the data model editor. This name can be modified by HChangeName before creating the data file.
- Directory of data file:
Directory defined during the file description in the data model editor. This directory can be modified by HChangeDir and HSubstDir before creating the data file.
Remark: If the UAC is enabled (Windows Vista and later), the data location is specific: the data will not be located in the application directory, but in a specific Windows directory. In this case, you must create the application data directory (you can get the path with fDataDirUser).
- The order of items created in the physical file is the physical order of items created in the analysis (and not the logical order).
- Content of the data file:
The created data file is empty, which does not mean that its size is null (the file contains a header describing its structure).
: If the data file already existed (same name, same directory), this data file is opened. If the hDelayedOpening
constant is specified, the data file will only be opened the first time it is accessed (optimizes the speed of HCreationIfNotFound
The password can be defined:
- when the data file is created or opened by HCreationIfNotFound.
- before the data file is created by HPass.Caution: The password is independent of data encryption. The data encryption must be configured during the file description in the data model editor ("Details" tab).
The password is not associated with a data file but with a database. This password must be specified during the connection (HConnect
Managing fatal errors when creating a data file
If a fatal error occurs when creating a data file, it may be interesting to continue the program while checking whether the data file was created or not. To do so, we recommend that you perform the following exception process:
WHEN EXCEPTION IN
Error("HFSQL error: " + HError())
Trace("The file is created")
Managing non-Latin character sets
If the hChangeCharset
constant is specified, the character set used in the data file will be the one specified by ChangeCharset
. Sorts, searches, ... on string keys (strings, characters, date and time) will be performed according to this character set.
The character set used can be modified by HIndex
Remark: the size of string items specified in the analysis is expressed in bytes and not in characters. Depending on the character set used, you may have to increase the item size (if the characters used are coded on 2 bytes for example).
Replication: Range of identifiers
The automatic identifiers for the files of subscriber replicas are using a range of identifiers that differs from the one used by the file of master replica and by the other files of subscriber replicas.
This range of automatic identifiers is written in the header of each data file (".FIC" extension).
This range is initialized:
For more details, see the consequences of implementing the replication
Priority for defining the location of log files
The location of log files is defined according to the following priority order:
- Location specified when creating the logged data file (HCreationIfNotFound).
- Location specified by HChangeLogDir.
- Location specified in the analysis.
- Location of the logged data file.
If another application uses HDeclareExternal
on a logged data file, the changes made by this application are saved in the log files specified in the header of the logged HFSQL data file.
Creating or opening an existing table
If the table already exists, the table is opened.
If the table does not already exist, the table is created. When creating a table, WINDEV and WEBDEV try to create the items in the OLE DB type corresponding to the HFSQL type. If this type is not supported, the HFSQL engine successively tries all the "compatible" OLEDB types until it finds a type that is supported by the OLEDB database.
HCreationIfNotFound does not return any error messages if an index cannot be added. The table is created without the index that is causing the problem. In this case, duplicates may be found in an item defined as unique key by WINDEV or WEBDEV if the external database does not support the unique keys.
Creating the data file from its description
The data file can be directly created from its description in the data model editor. To do so, select "Create the data file" from the popup menu of the data file (in the analysis graph) and select the directory in which the data file must be created.
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iniresult is string = INIRead("APP","VERSAO","",fDataDir() + ["\"] +"CONFIG.INI")
IF (Num = 1 AND iniresult = "") OR (Num = 1 AND iniresult = 0) THEN
INIWrite("APP","VERSAO","2",fDataDir() + ["\"] +"CONFIG.INI")
fDelete(fDataDir() + ["\"] +"t000_config.fic")
fDelete(fDataDir() + ["\"] +"t000_config.ndx")
fDelete(fDataDir() + ["\"] +"t000_config.mmo")
HModifyStructure("*",hmsBackgroundTask) // 1.º CODE ORDER
HCreationIfNotFound("*","app488640") // 2.º CODE ORDER