- Search item
- Browsing queries
- Locks
- Memos
- Password
- Native XML access
- Various
HReadFirst (Function)
 No disponible con este tipo de conexión
Positions on the first file record according to a search item. The record is read and the HFSQL variables are updated (Customer.Name for example, which means the Name item of Customer file). The reading is performed from the lowest value to the greatest value of search item (see the notes for more details). In most cases, HReadFirst is used to position in the data file in order to perform a read loop with HReadNext. Several cases may occur after the call to HReadFirst: - the data file is empty or no record corresponds to the filter (defined by HFilter): no reading is performed and HOut returns True.
- the function tries to read a record that is already locked in read mode: no reading is performed, HErrorLock returns True and HOut returns True.
 Access by JDBC: The management of locks is not available for the databases accessed by JDBC.
This function can be used with the data files, HFSQL views or queries.  Versiones 18 y posteriores Nueva funcionalidad versión 18señalar: A partir de la versión 19, HFSQL es el nuevo nombre de HyperFileSQL. Versiones 21 y posteriores Nueva funcionalidad versión 21
HReadFirst(Customer, Name)
WHILE HOut(Customer) = False
// Process the record
HReadNext(Customer, Name)
END
Sintaxis
<Result> = HReadFirst([<File Name> [, <Name of Search Item>] [, <Options>]])
<Result>: Boolean Corresponds to: - False if an error occurred. In this case, HError returns an integer other than 0. HErrorInfo returns more details about the error. The record is not read.
- the value of HFound in the other cases (the record can be read, even if <Result> returns False).
<File Name>: Optional character string (with or without quotes) Name of data file, HFSQL view or query used. If this parameter corresponds to an empty string (""), HReadFirst handles the last data file used by the last function for HFSQL management (starting with the letter H). <Name of Search Item>: Optional character string (with or without quotes) Name of item used to browse the data file or view (this parameter is ignored by the queries). If this name is not specified, HReadFirst will use:- For a data file: the last search item used on this file by the last function for HFSQL management (starting with the letter H). If this item does not exist, the best search item is automatically used.
- For a query: the ORDER BY of query if it exists, otherwise the last item used.
- For a view: the sort item of view (if it exists), otherwise the last item used.
<Options>: Optional constant Used to configure:- the lock performed on the record read by HReadFirst
- whether the filter that was defined must be taken into account.
| | | hLockNo | No lock (even if HStartLock was called): the record can be read or modified by another application during the reading.
| | hLockWrite | Lock in write mode: the record currently read can be read by another application but it cannot be modified by another application.
| | hLockReadWrite | Lock in read/write: the record currently read cannot be read or modified by another application.
| Versiones 17 y posterioreshForwardOnly Nueva funcionalidad versión 17hForwardOnly hForwardOnly | | | 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, poor performance may occur on huge data files.
| | hNoRefresh | |
Observaciones If the search item is a key, HReadFirst reads the record with the lowest key value. The sort order is the one that was specified in the analysis for this key. If duplicates are found, HReadFirst reads the first "duplicate" record according to the sequence of record numbers. If the search item is not a key, HReadFirst reads the first active record. When browsing the file, the records will be sorted according to their record number. In this case, the selected search item will appear in red in the code editor and a warning will be displayed in the "Code" pane. The memos associated with the record can be automatically read (or not) when reading the record. HSetMemo is used to customize this automatic reading. If the memos are supported, the associated text memos are read when the record is read. The binary memos are read only when they are explicitly used ( HExtractMemo). If HReadFirst is the first function that handles the specified data file, the password is checked when opening the data file. If the password is incorrect, HErrorPassword returns True and HOut returns True. - The current record number is returned by HRecNum.
- HChangeKey is used to modify the search key while being positioned on the current record.
- To optimize the time of the first browses performed on a file, use HOptimize on this data file.
Esta página también está disponible para…
|
|
|