|
|
|
|
|
|
|
|
|
|
- Read operation based on a key
- Comparison between HPrevious and HReadPrevious
- Miscellaneous
- Locks
HPrevious (Function) In french: HPrécédent
 Not available with this kind of connection
Sets the position on the previous record of the 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 functions handling the current record number by default (functions HDelete, HRead, HModify, ...), the value of this number is not updated: you must use the HRecNum() function. For example: do not:
but
HDelete(Customer, HRecNum())
Values in the browse item are read in descending order (for more details, see the remarks). Warning: Recording loaded into memory is not modified. The HFSQL variables (for example Customer.Name, i.e. the Name item of the Customer file) are not updated. Generally, HPrevious sets the position in the data file during a loop operation. Several cases may occur after the call to HPrevious: - the data file is empty or there is no record corresponding to the filter (defined by HFilter): function HOut returns True.
- the function attempts to block a record already blocked in playback: function HErrorLock returns True and function HOut returns True.
 JDBC access: lock management is not supported for databases that are accessed through JDBC.
HLast(Customer, Name)
WHILE HOut() = False
HPrevious(Customer, Name)
END
Syntax
<Result> = HPrevious([<Data file> [, <Search key item>] [, <Options>]])
<Result>: Boolean - True if the position was set,
- False if an error occurs. This problem can be caused by:
- or a positioning problem (empty data file, etc.): function HFound returns Faux 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 HFSQL data file used. If this parameter corresponds to an empty string, HPrevious will use the last data file used by the last HFSQL management 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, HPrevious will use the last browse item used on this 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 and the management of duplicates performed on the record selected by HPrevious: | | | hDistinct | If there are any duplicates, sets the position on a single record of the duplicates. This parameter is taken into account only if the iteration is performed on a key item.
By default, all duplicates are iterated over. | | hLockNo | No blocking: the recording can be played back 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 cannot be modified by another application. |
Remarks Read operation based on a key HPrevious sets the position on the record with the greatest key value. The sort order taken into account is the one specified in the analysis for this key. Comparison between HPrevious and HReadPrevious The function HPrevious function does not play the recording: the HPrevious is therefore faster than function HReadPrevious.
This page is also available for…
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|