HWrite (Function)

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Help / WLanguage / Managing databases / HFSQL / HFSQL functions

Managing automatic identifiers
Writing deleted or crossed records
Version of the data file after a write operation
Managing binary memos
If you use HWrite with a Hyper File 5.5 database
Browsing and writing a record

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HWrite (Function)

In french: HEcrit

Not available with this kind of connection

Writes a record into a data file without updating the indexes corresponding to all keys used in the data file. The memos are added if necessary (if the management of memos is enabled, HSetMemo).

After the call to HWrite:

integrity and duplicate errors are not checked.
if a lock problem occurs (attempt to modify a locked record), HErrorLock returns True and the record is not modified.
the current record number is modified: the current record corresponds to the written record.

Remarks:

To update the indexes during a write operation, use HAdd or HModify.
HWrite and HModify are equivalent. The indexes on the database are updated.
If a key value is modified with HWrite, the index will no longer be consistent. It must be re-indexed (HIndex).
This function can be used to write a record in a selection made by a query (query executed with the constant hWithFilter constant only).

Example

// Écriture d'un enregistrement à la fin d'un fichier de données
HWrite(Client, HNbRec() + 1)

Syntax

<Result> = HWrite([<Data file> [, <Record number> [, <Options>]]])

<Result>: Boolean

True if the writing was performed in the data file,
False in the event of an error (blocking, etc.): the record is not modified. HError is used to identify the error.

<Data file>: Optional character string

Name of the data file used. If this name is not specified, HWrite will use the last data file used by the last HFSQL function (function starting with "H").

<Record number>: Optional integer

Number of the record to write. The record loaded in memory is re-written on the specified record.
If this number is greater than the total number of records in the data file, intermediate deleted records will be created in order for the sequential reading of the data file (HRead) to be consistent.
If this parameter is not specified (equal to 0 or to the hCurrentRecNum constant), HWrite modifies the current record in the data file.
HWrite modifies the current record only. You cannot specify a record number other than the current one (to specify the current record number, use the hRecNumCurrent constant).

<Options>: Combination of optional constants

Configures:
automatic identifier calculation mode For details of how to manage the automatic identifier when adding a record, see Managing the automatic identifier during an addition.
hForceIDAuto The automation ID is not calculated at the time of writing: the ID value will be the one stored at the time of writing.
hRecalculateIDAuto The automatic identifier of the record will be re-calculated during the write operation. This constant has priority over hForceIDAuto and hSetIDAuto.
hSetIDAuto The automation ID is not calculated at the time of writing: the ID value will be that stored at the time of writing.
The next identifier value calculated by the HFSQL engine will correspond to the largest identifier value in the +1 data file.
hWriteDefault
(Default value) If the written record is not a deleted record, the automatic identifier (if it exists) of the record in the data file is re-used.
If the written record is a deleted record, a new automatic identifier is calculated for the record.
The hWriteDefault constant is ignored if hWriteDefault is specified with one of the other constants.

A WLanguage error is generated if the three constants (hForceIDAuto, hSetIDAuto and hRecalculateIDAuto) are used at the same time.
the lock mode applied to the record.
If no lock constant is specified, the record is not locked.
hLockNo
(Default value) No blocking: the written record will not be blocked.
hLockReadWrite Read/write lock: the written record will be locked in read and write mode. This record cannot be read or modified by another application. Only the current application can modify it, read it or unlock it.
hLockWrite Lock in write mode: the written record will be locked in write mode. This record can be read by another application but it cannot be modified by another application. Only the current application can modify it or unlock it.

Lock options will have no effect if the OLE DB provider or Native Connector (also called Native Access) does not support locks.

<Options> is ignored.

Remarks

Managing automatic identifiers

By default, the "automatic identifier" item is automatically updated when a record is added into a data file.

The hForceIDAuto and hSetIDAuto constants are used to modify the default behavior of the automatic identifier.

For more details on automatic identifiers for new records, see Managing the automatic identifier.

Special cases

If the database generates an automatic identifier, the HFSQL engine keeps this value. If the hForceIDAuto or hSetIDAuto constant is specified, the HFSQL engine replaces the generated value by the desired value.
Note The constant hForceIDAuto is equivalent to hFixeIDAuto: the automatic identifier calculated by the HFSQL engine the next time a file is added will be unique in the data file.
If no automatic identifier is generated by the database, the HFSQL engine generates the value and assigns it to the automatic identifier.

Writing deleted or crossed records

If the record number corresponds to a crossed record or to a deleted record, this record is re-enabled.

Version of the data file after a write operation

If the record was written (no lock problem, etc.), the data file version number is modified. To get the version number, use HVersion.

Managing binary memos

When a record is modified, the memos are modified if necessary (if the management of memos is enabled by HSetMemo).
Reminder To initialize a binary memo item, use function HLinkMemo.

If you use HWrite with a Hyper File 5.5 database

The TEXT items are automatically filled with space characters.

Browsing and writing a record

If the write operation is performed during a browse, the record written will be visible in the current browse only. If other browse operations have been defined on this database, the record written will only be visible once these browse operations have been reinitialized.

Component: wd300hf.dll