HPrevious (Function)

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Read operation according to a key
Comparison between HPrevious and HReadPrevious
Miscellaneous
Locks

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HPrevious (Function)

In french: HPrécédent

Not available with this kind of connection

Positions on the previous file record 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, HPrevious 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 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 performs a generic search.

Values in the browse item are read in descending 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, 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.
Access by JDBC: The management of locks is not available for databases accessed by JDBC.

Example

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

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 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 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.
hLockNo No lock: the record can be read or modified by another application.
hLockReadWrite Lock in read/write: 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 by another application.
Access by JDBC: This parameter is ignored.
The lock options will have no effect if the locks are not supported by the OLE DB provider or by the Native Connector.
The lock options specified by HPrevious will be ignored. The lock mode specified by HFirst or HLast 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.
For Native Oracle Connector, a different lock mode can be specified for each record. However, if a transaction was started by SQLTransaction before setting the lock, the lock will only be released at the end of the transaction (SQLTransaction with the sqlCommit or sqlRollBack constant).
The lock options are ignored. Use the lock functions (HLockRecNum) kept for backward compatibility.