Positions on the previous file record according to a browse 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:
but
HDelete(Customer, HRecNum())
The reading is performed from the lowest to the greatest value of the browse item (see the 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,
HPrevious sets the position in the data file to browse through the records that correspond to a condition.
HNext is used to position on the next record corresponding to the condition.
Several cases may occur after the call to HPrevious:
- 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, HPrevious is used to perform a generic search.
Versions 15 and later
New in version 15Versions 17 and later New in version 17 Versions 18 and later New in version 18 Remark: From version 19, HFSQL is the new name of HyperFileSQL. Versions 21 and later New in version 21 The read operation is performed from the greatest to the lowest 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, HPrevious is used to position in the data file during a browse loop.
Several cases may occur after the call to HPrevious:
- 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.
Locks are managed only on HFSQL Client/Server data files or on data files handled by a Native Connector. An 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 New in version 15 Versions 17 and later New in version 17 Versions 18 and later New in version 18 Remark: From version 19, HFSQL is the new name of HyperFileSQL. Versions 21 and later New in version 21
HLast(Customer, Name)
WHILE HOut() = False
// Process the record
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 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.
<Data file>: Optional character string (with or without quotes)
Name of HFSQL data file used. If this parameter corresponds to an empty string, HPrevious handles the last data file used by the last function for HFSQL management (starting with the letter H).
<Search 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, 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: | |
| hLockWrite | Lock in write mode: the selected record can be read by another application but it cannot be modified by another application. |
| hLockReadWrite | Lock in read/write: the selected record cannot be read or modified by another application. |
| hLockNo | No lock (even if HStartLock was called): the record can be read or modified by another application. |
| hDistinct | If duplicates are found, it is used to position on a single record among the duplicates. This parameter is taken into account only if the browse is performed on a key item.
By default, all the duplicates are browsed. |
Remarks
Read operation according to a key
HPrevious 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.
Comparison between HPrevious and HReadPrevious
HPrevious does not read the record: therefore,
HPrevious is faster than
HReadPrevious.