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  • Read operation according to a key item or not
  • Memos
  • Browsing the records corresponding to a condition
  • Modifying the value of search key
  • Locks
  • Various
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Stored procedures
Positions on next 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 browse item (see remarks for more details).
HReadNext is used to position in the data file during a browse loop. This function can only be run:
Several cases may occur after the call to HReadNext:
  • the 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 lock a record that is already locked in read-only: no reading is performed, HErrorLock returns True and HOut returns True.





This function can be used with the data files, HFSQL views or queries. Remark: From version 19, HFSQL is the new name of HyperFileSQL.
Example
HReadFirst(Customer, Name)
WHILE HOut() = False
// Process the record
HReadNext(Customer, Name)
END
Syntax
<Result> = HReadNext([<Data file> [, <Browse 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).
<Data file>: Optional character string (with or without quotes)
Name of data file, view or query used. If this parameter corresponds to an empty string (""), HReadNext uses the last data file used by the last HFSQL management function (function starting with "H").
<Browse item>: Optional character string (with or without quotes)
Name of item used to browse the data file, view or query. If this name is not specified, HReadNext will use:
  • For a data file: 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.
  • 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 (or combination of constants)
Used to configure:
  • the lock performed on the record read by HReadNext
  • the management of duplicates. By default, all the duplicates are browsed.
hLockNoNo lock (even if HStartLock was called): the record can be read or modified by another application during the reading.
hLockWriteLock in write mode: the record currently read can be read by another application but it cannot be modified by another application.
hLockReadWriteLock in read/write: the record currently read cannot be read or modified by another application.
hDistinctIf duplicates are found, this constant allows you to read a single record among the duplicates. This parameter is taken into account only if the browse is performed on a key item.

OLE DBNative Connectors (Native Accesses) This constant is ignored.
OLE DBNative Connectors (Native Accesses) Lock options will have no effect if the OLE DB provider or Native Connector (also called Native Access) does not support locks.
OLE DB The lock options specified by HReadNext will be ignored. The lock mode specified by HReadFirst or HReadLast will remain effective during the calls to HReadNext and HReadPrevious.
To modify the lock mode, you must use:
Remarks

Read operation according to a key item or not

If the item is a key, HReadNext reads the record with the greatest key value. The sort order is the one that was specified in the analysis for this key.
Remark: In a search loop (HReadSeekFirst for example), when HReadNext reads the record with the greatest key value, HFound allows you to find out whether the record corresponds (or not) to the sort criterion. If the item is not a key, HReadNext reads the next active record. When browsing the data 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.
Remark: The automatic completion proposes the key items only.

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).

Browsing the records corresponding to a condition

In most cases, HReadSeek, HReadSeekFirst and HReadSeekLast are used to position in the data file to perform a browse loop among the records corresponding to a condition. HReadNext and HReadPrevious are used to read the next or previous record corresponding to the condition:
  • if the item used is a key, HReadNext will read the next records corresponding to the values greater than or equal to the sought value.
  • if the item used is not a key, HReadNext will read the next records corresponding to the values equal to the sought value.
To ignore the search while going to the next or previous record, use one of the following functions:
Caution: if a browse must be performed by HReadNext, the initial search (HReadSeek, HReadSeekFirst, HReadSeekLast) must not use the hLimitParsing constant.

Modifying the value of search key

If the value of search key is modified before the call to HReadNext, the current record may be read again in the rest of browse by HReadNext.
Indeed, the modification of search item updates the index key of file. This modification is taken into account when reading the next records.
This remark is also valid when using HReadNext without search key a sorted query (ORDER BY).
Reports and QueriesHFSQLHFSQL Client/ServerHyper File 5.5OLE DBNative Connectors (Native Accesses)

Locks

By default (<Options> not specified), no lock operation is performed on the record.
If a lock is specified (hLockWrite or hLockReadWrite constants), the record will be read only if this record is not already locked.
There is no need to specify a lock parameter if the data file is locked by HStartLock: the lock specified by HStartLock is automatically taken into account. To ignore the lock specified by HStartLock, use the hLockNo constant.
OLE DBNative Connectors (Native Accesses) The lock options will have no effect if the locks are not supported by the OLE DB provider or by the Native Connector.

Various

  • The current record number is returned by HRecNum.
  • HChangeKey is used to modify the search key while remaining positioned on the current record.
  • To optimize the time of the first browses on a data file, use HOptimize on this data file.
Component : wd250hf.dll
Minimum version required
  • Version 9
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