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- Browse item
- Browsing queries
- Locks
- Memos
- Password
- Native XML Connector
- Miscellaneous
HReadFirst (Function) In french: HLitPremier
Not available with this kind of connection
Positions on the first file record according to a browse item. The record is read and the HFSQL variables are updated (Customer.Name for example, which means the Name item of Customer file). Values in the browse item are read in ascending order (for more details, see the remarks). In most cases, HReadFirst is used to set the 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 read operation is performed, HErrorLock returns True and HOut returns True.
The management of locks is not available. Access by JDBC: The management of locks is not available for databases accessed by JDBC.
This function can be used with the data files, HFSQL views or queries.
HReadFirst(Customer, Name)
WHILE HOut(Customer) = False
HReadNext(Customer, Name)
END
Syntax
<Result> = HReadFirst([<Data file> [, <Browse item>] [, <Options>]])
<Result>: Boolean Corresponds to: - False if an error occurs. 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).
<Data file>: Optional character string Name of data file, HFSQL view or query used. If this parameter is an empty string (""), HReadFirst manipulates the last data file used by the last HFSQL function (function starting with "H"). <Browse item>: Optional character string Name of item used to loop through 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 browse 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 browse 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 the view (if it exists), otherwise the last item used.
<Options>: Optional constant Used to configure:- the lock set on the record read by HReadFirst
- whether the filter that was defined must be taken into account.
| | hForwardOnly | | 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 search key optimized for the filter. Caution: in this case, performance issues may arise for large files.
| hLockNo | No lock: the record can be read or modified by another application during the reading.
| hLockReadWrite | Lock in read/write mode: the record currently read cannot be read or modified by another application.
| hLockWrite | Lock in write mode: the record currently read can be read by another application but it cannot be modified.
| hNoRefresh | |
Remarks Browse item If the browse item is a key, HReadFirst reads the record with the lowest key value. The sort order taken into account is the one 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 browse 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 browse item will appear in red in the code editor and a warning will be displayed in the "Code" pane. Memos The memos associated with the record can be automatically read (or not) when reading the record. HSetMemo is used to customize this automatic read operation. 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). Password If HReadFirst is the first function that handles the specified data file, the password is checked when the opening data file. If the password is incorrect, HErrorPassword returns True and HOut returns True. Miscellaneous - HRecNum returns the current record number.
- HChangeKey changes the search key while keeping the position on the current record.
- To improve the first browse times on a file, use HOptimize on this data file.
- This function replaces HReadFirstLock and HReadFirstNoLock, which were kept for compatibility with WINDEV 5.5.
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