HFirst (Function)

Positions on the first file record according to the specified search item. The record is not read. The number of the current record is modified when it is returned by HRecNum. For the functions that handle the current record number (HDelete, HRead, HModify, ...), the value of this number is not updated: you must use HRecNum(). For example: not to do:

HDelete(Customer)

but

HDelete(Customer, HRecNum())

The read operation is performed from the lowest to the greatest value of the browse item (see remarks for more details).

Caution: The record loaded in memory is not modified. The HFSQL variables (Customer.Name for example, which means the Name item of Customer file) are not updated.

In most cases, HFirst is used to position in the data file in order to perform a read loop with HNext.

Several cases may occur after the call to HFirst:

the data file is empty or there is no record corresponding to the filter (defined by HFilter): HOut returns True.
the function tries to lock a record that is already locked in read-only: HErrorLock returns True and HOut returns True.
The management of locks is only performed on HFSQL Client/Server data files or data files handled by a Native Access. A HFSQL Mobile record cannot be locked. Indeed, the operating system of Pocket PC does not allow you to lock records.
Access by JDBC: The management of locks is not available for the databases accessed by JDBC.

Versions 15 and later

This function is now available for Android applications.

New in version 15

This function is now available for Android applications.

Versions 17 and later

This function is now available for iPhone/iPad applications.

New in version 17

This function is now available for iPhone/iPad applications.

Versions 18 and later

This function is now available in Android Widget mode.

This function is now available in Windows Store apps mode.

New in version 18

This function is now available in Android Widget mode.

This function is now available in Windows Store apps mode.

This function is now available in Android Widget mode.

This function is now available in Windows Store apps mode.

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

Versions 21 and later

This function is now available in Universal Windows 10 App mode.

New in version 21

This function is now available in Universal Windows 10 App mode.

Example

HFirst(Customer, Name)
WHILE HOut() = False
// Process the record
HNext(Customer, Name)
END

Syntax

<Result> = HFirst([<File name> [, <Name of browse key item>] [, <Options>]])

<Result>: Boolean

True if the positioning was performed,
False if an error occurred. This problem can be caused by:
a positioning problem (empty data file, ...): HFound returns False and HError returns 0.
an error: HError returns an integer other than 0. HErrorInfo returns more details.

<File name>: Optional character string (with or without quotes)

Name of data file used. If this parameter corresponds to an empty string (""), HFirst handles the last data file used by the last function for HFSQL management (starting with the letter H).

<Name of browse key item>: Optional character string (with or without quotes)

Name of key item used to browse the data file. If this name is not specified, HFirst handles the last search item used on this data file by the last function for HFSQL management (starting with the letter H). If this item does not exist, the best browse item is automatically used.

<Options>: Optional constant

Configures the lock performed on the record selected by HFirst:
hLockNo No lock (even if HStartLock was called): the record can be read or modified by another application.
Access by JDBC: This constant is not available.
hLockWrite Lock in write mode: the selected record can be read by another application but it cannot be modified by another application.
Access by JDBC: This constant is not available.
hLockReadWrite Lock in read/write: the selected record cannot be read or modified by another application.
Lock in write mode: the selected record can be read by another application but it cannot be modified by another application. Equivalent to hLockWrite.

Access by JDBC: This constant is not available.
hKeepFilter The filter implemented by HFilter will be taken into account, even if the search key is not optimized for the filter. Reminder: HFilter returns the search key optimized for the filter.
Caution: In this case, lack of performances may occur on huge data files.
This variable cannot be used.
hNoRefresh
The table or query content will not be refreshed. All the saved positions are stored. If this parameter is not specified, HFirst reinitializes the browse for the specified item: the content of table or query is refreshed with the data found in the OLE DB database. All the saved positions are lost. The position will be restored according to the value of best item.
Note: The browses and the positions saved on the other items are not affected.
The management of locks is only performed on HFSQL Client/Server data files or data files handled by a Native Access. A HFSQL Mobile record cannot be locked. Indeed, the operating system of Pocket PC does not allow you to lock records.
Access by JDBC: The management of locks is not available for the databases accessed by JDBC.
The lock options will have no effect if the locks are not supported by the OLE DB provider or by Native Access.
The lock mode specified by HFirst will remain effective during the calls to HPrevious and HNext.
To modify the lock mode, you must use:
HSeekFirst or HSeekLast,
HFirst or HLast.
HLockRecNum or HUnlockRecNum.
Oracle: a different lock mode can be specified for each record. However, if a transaction was started by SQLTransaction before implementing the lock, the lock will only be released at the end of the transaction (SQLTransaction associated with SQLCommit or SQLRollback).
The lock options are ignored. Use the lock functions (HLockRecNum) kept for backward compatibility.

Remarks

Read operation according to a key

HFirst positions on the record with the smallest key value.

The sort order is the one that was specified in the analysis for this key.

If duplicates are found, HFirst positions on the first "duplicate" record according to the sequence of record numbers.

Checking the password

If HFirst is the first function that handles the specified data file, the password is checked when opening the data file.

If the password is incorrect, HErrorPassword returns True and HOut returns True.

Various

The current record number is returned by HRecNum.
HChangeKey is used to modify the search key while being positioned on the current record.

Comparing HReadFirst and HFirst

HFirst does not read the record: therefore, HFirst is faster than HReadFirst.

Locks

By default (<Options> not specified), no lock operation is performed on the record.

If a lock is requested (hLockWrite or hLockReadWrite constant), the positioning on the record will be performed only if this record is not already locked.

There is no need to specify a lock parameter if the data file is locked by HStartLock: the lock specified by HStartLock is automatically taken into account. To ignore the lock performed by HStartLock, use the hLockNo constant.

Component : wd240hf.dll