HLast (Function)

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Read operation based on a key
Checking the password
Miscellaneous
Comparing HReadLast and HLast
Locks

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HLast (Function)

In french: HDernier

Not available with this kind of connection

Sets the position on the last record of a data file according to a browse item. The record is not read.
The number of the current record is modified only when it is returned by HRecNum. For the functions that handle the current record number (HDelete, HRead, HModify, etc.), the value of this number is not updated: you must use HRecNum(). For example: not to do:

HDelete(Customer)

but

HDelete(Customer, HRecNum())

Values in the browse item are read in ascending order (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, HLast sets the position in the data file to loop through the records that match a condition. HNext is used to position on the next record corresponding to the condition.

Several cases may occur after the call to HLast:

a record corresponding to the condition was found: HFound returns True
the data file is empty or there is no record corresponding to the condition: HOut returns True

Remarks:

By default, HSeekFirst and HSeekLast are used to perform an exact-match search.
By default, HLast performs a generic search.

The highest value in the browse item is read (for more details, see remarks).

Caution: The record loaded in memory is not modified. HFSQL variables (e. g. Customer.Name, or the Name item of the Customer data file) are not updated.

In most cases, HLast is used to set the position in the data file in order to perform a read loop with HPrevious.

Several cases may occur after the call to HLast:

the data file is empty or no record corresponds 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.

Management of locks not available in SQLite databases.

Example

// Browse a data file from the last record
HLast(Customer, Name)
WHILE NOT HOut()
	// Process the record
	HPrevious(Customer, Name)
END

Syntax

<Result> = HLast([<Data file>] [, <Search key item> [, <Options>]])

<Result>: Boolean

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

<Data file>: Optional character string

Name of the data file used. If this parameter is an empty string (""), HLast manipulates the last data file used by the last HFSQL function (function starting with "H").

<Search key item>: Optional character string

Name of the key item used to loop through the data file. If this name is not specified, HLast will use the last browse item used on this data file by the last HFSQL management function (function starting with "H"). If this item does not exist, the best browse item is automatically used.

<Options>: Optional constant

Configures the lock set on the record selected by HLast:
hKeepFilter The filter set 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, performance issues may arise for large files.
hLockNo No lock: the record can be read or modified by another application.
hLockReadWrite Lock in read/write mode: the selected record cannot be read or modified by another application.
hLockWrite Lock in write mode: the selected record can be read by another application but it cannot be modified.
hNoRefresh
The table or query content will not be refreshed. All the saved positions are stored.
If this parameter is not specified, HLast 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.
Remark: The browses and the positions saved on the other items are not affected.

The lock options will have no effect if the locks are not supported by the OLE DB provider or by the Native Connector.
Management of locks not available in SQLite databases.

Remarks

Read operation based on a key

HLast sets the position on the record with the greatest key value.

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

If duplicates are found, HLast sets the position on the first "duplicate" record according to the sequence of record numbers.

Checking the password

If HLast 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.

Miscellaneous

HRecNum returns the current record number.
HChangeKey changes the search key while keeping the position on the current record.

Comparing HReadLast and HLast

HLast does not read the record: therefore, HLast is faster than HReadLast.

Locks

By default (<Options> not specified), the record is not locked.

If a lock is requested (hLockWrite or hLockReadWrite constant), the position will be set on the record only if it is not already locked.

Component: wd300hf.dll