- Read operation according to a key item or not
- Browsing the records corresponding to a condition
- Modifying the value of search key
In french: HLitSuivant
Not available with this kind of connection
Sets the position on the next data 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
Values in the browse item are read in ascending order (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 read operation is performed, HErrorLock returns True and HOut returns True.
WHILE HOut() = False
// Process the record
<Result> = HReadNext([<Data file> [, <Browse item>] [, <Options>]])
- 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
Name of data file, view or query used. If this parameter is an empty string (""), HReadNext 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 browse the data file, view or query. If this name is not specified, HReadNext will use:
- For a data file: 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.
- 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 set on the record read by HReadNext
- the management of duplicates. By default, all the duplicates are browsed.
|hLockNo||No lock: 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.|
|hDistinct||If 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.|
This constant is ignored.
Lock options will have no effect if the OLE DB provider or Native Connector (also called Native Access) does not support locks.
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.
: 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 browse 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 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
are used to position in the data file to perform a browse loop among the records corresponding to a condition. HReadNext
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:
Modifying the value of search key
If the value of the browse item is modified before HReadNext is used, the current record can be read again by HReadNext in the rest of the browse.
Indeed, modifying the browse item updates the file index key. 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).
- The current record number is returned by HRecNum.
- HChangeKey is used to modify the search key while remaining positioned on the current record.
- To improve the first browse times on a data file, use HOptimize on this data file.
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