<Source>.Previous (Function)

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Read operation based on a key
Comparison between <Source>.Previous and .ReadPrevious
Miscellaneous
Locks

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<Source>.Previous (Function)

In french: <Source>.Précédent

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 <Source>.RecNum. For functions handling the current record number by default (functions <Source>.Delete, <Source>.Read, <Source>.Modify, ...), the value of this number is not updated: you must use the <Source>.RecNum() function. For example: do not:

Client.Supprime()

but

Client.Supprime(Client.NumEnr())

Values in the browse item are read in descending order (for more details, see the remarks).

Attention: Record 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, <Source>.Previous sets the position in the data file during a loop operation.

Several cases may occur after the call to <Source>.Previous:

the data file is empty or there is no record corresponding to the filter (defined by <Source>.Filter): function <Source>.Out returns True.
the function attempts to block a record already blocked in play mode: function HErrorLock returns True and function <Source>.Out returns True.

Example

Client.Dernier(Nom)
WHILE Client.EnDehors() = False
	// Traitement de l'enregistrement
	Client.Précédent(Nom)
END

Syntax

<Result> = <Source>.Previous([<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 <Source>.Found returns False and HError returns 0.
an error: HError returns an integer other than 0. HErrorInfo returns more details.

<Source>: Type corresponding to the specified source

Name of the HFSQL data file used.

<Search key item>: Optional character string

Name of the key item used to loop through the data file. If this name is not specified, <Source>.Previous 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 <Source>.Previous:
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 Record 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.

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 <Source>.Previous will be ignored. The lock mode specified by <Source>.First or <Source>.Last will remain effective during the calls to <Source>.Previous and <Source>.Next.
To change the lock mode, use:
<Source>.SeekFirst or <Source>.SeekLast.
<Source>.First or <Source>.Last.
<Source>.LockRecNum or <Source>.UnlockRecNum.
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 (<Source>.LockRecNum) kept for backward compatibility.

Remarks

Read operation based on a key

<Source>.Previous 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 <Source>.Previous and <Source>.ReadPrevious

The function <Source>.Previous function does not play the Record: the <Source>.Previous is therefore faster than function <Source>.ReadPrevious.

Miscellaneous

<Source>.RecNum returns the current record number.

<Source>.ChangeKey changes the search key while keeping the position on the current record.

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