- Read operation according to a key
- Checking the password
- Various
- 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 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, HFirst 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 HFirst: - 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, HFirst 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 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 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 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 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
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 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 data file used. If this parameter corresponds to an empty string (""), HFirst will use the last data file used by the last HFSQL management function (function starting with "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 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: | | | 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 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, performance issues may arise for large 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 sets the position 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 remaining positioned on the current record.
Comparison between 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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