- Read operation according to a key
- Checking the password
- Various
- Comparing HReadFirst and HFirst
- Locks
HFirst (Function) In french: HPremier
 Not available with this kind of connection
Positions on the first file record according to the specified search item. The record is not read.
The number of the current record is only changed when it is returned by the HRecNum function. For functions that manipulate by default the number of the current record (functions HDelete, HRead, HModify,...), the value of this number is not updated: you must use HRecNum(). For example: not to do:
HDelete(Customer, HRecNum())
The read operation is performed from the lowest to the greatest 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, HFirst is used to 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 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.
 The management of locks is only performed on HFSQL Client/Server data files or data files handled by a Native Access. 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 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
HFirst(Customer, Name)
WHILE HOut() = False
// Process the record
HNext(Customer, Name)
END
Syntax
<Result> = HFirst([<Data file> [, <Search key item>] [, <Options>]])
<Result>: Boolean - True if the positioning was performed,
- 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 data file used. If this parameter corresponds to an empty string (""), HFirst 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, HFirst handles the last search item used on this data file by the last function for HFSQL management (starting with the letter H). If this item does not exist, the best browse item is automatically used. <Options>: Optional constant Configures the lock performed on the record selected by HFirst: | | | hLockNo | No lock (even if HStartLock was called): the record can 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.
| | hLockReadWrite | Lock in read/write: the selected record cannot be read or modified by another application.
| | hKeepFilter | The filter implemented by HFilter will be taken into account, even if the search key is not optimized for the filter. Reminder: HFilter returns the search key optimized for the filter.
Caution: In this case, lack of performances may occur on huge data files.
| | hNoRefresh | |
Remarks Read operation according to a key HFirst positions on the record with the smallest key value. The sort order is the one that was specified in the analysis for this key. If duplicates are found, HFirst positions on the first "duplicate" record according to the sequence of record numbers. Various - The current record number is returned by HRecNum.
- HChangeKey is used to modify the search key while being positioned on the current record.
Comparing HReadFirst and HFirst HFirst does not read the record: therefore, HFirst is faster than HReadFirst.
This page is also available for…
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| | O filetoarray se não tiver antes dele um hfilter coloca no array a tabela inteira e se colocar o hfilter, traz só o registro. exemplos:
//assim vai trazer só o registro atual
HFilter(RADFileA,RADFileA.IDRADFileA,gnID)
FileToArray(garr_RADFileA_Depois,RADFileA,RADFileA.IDRADFileA)
//vai trazer todos os registros
FileToArray(garr_RADFileA_Depois,RADFileA,RADFileA.IDRADFileA)
DICA:
Voce pode atribuir uma Classe de um arquivo a um array assim:
garr_RADFileA_Antes is array of CMRADFileA
garr_RADFileA_Depois is array of CMRADFileA |
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