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- Read operation based on a key
- Checking password
- Miscellaneous
- Comparison between HReadFirst and HFirst
- Locks
HFirst (Function) In french: HPremier
 Not available with this kind of connection
Sets the position on the first record of a data file according to the specified 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 ascending order (for more details, see the remarks). Caution: The record loaded into memory is not modified. HFSQL variables (e.g. Client.Name, i.e. the Nom field in the Clientfile) are not updated. In most cases, HFirst is used to set the position in the data file in order to perform a read loop with HNext. Several cases may occur after the call to HFirst: - the data file is empty or there is no record corresponding to the filter (defined by function 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.
HFirst(Customer, Name)
WHILE HOut() = False
HNext(Customer, Name)
END
Syntax
<Result> = HFirst([<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 function 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 (""), HFirst 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, HFirst 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 HFirst: | | | 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 optimized search key for the filter.
Caution: In this case, on large data files, performance problems may occur..
| | 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..
| | hNoRefresh | |
Remarks Read operation based on a key HFirst positions on the record with the smallest key value. The sort order taken into account is the one specified in the analysis for this key. If duplicates are found, HFirst sets the position on the first "duplicate" record according to the sequence of record numbers. Miscellaneous - HRecNum returns the current record number.
- HChangeKey changes the search key while keeping the position on the current record.
Comparison between HReadFirst and HFirst The function HFirst function does not play the recording: the HFirst is therefore faster than function HReadFirst.
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