Sets the position on the last data file record whose value for a specific item is less than or equal to a sought value.
The record is not read.
The number of the current record is modified only when it is returned by
HRecNum. For the functions that handle the current record number (
HDelete,
HRead,
HModify, etc.), the value of this number is not updated: you must use
HRecNum(). For example: not to do:
but
HDelete(Customer, HRecNum())
Values in the browse item are read in ascending order (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,
HSeekLast sets the position in the data file to loop through the records that match a condition.
HNext is used to position on the next record corresponding to the condition.
Several cases may occur after the call to HSeekLast:
- 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, HSeekLast performs a generic search.
The reading is performed from the lowest value to the greatest value of search item (see the notes 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, HSeekLast sets the position in the data file to loop through the records that match a condition.
Several cases may occur after the call to HSeekLast:
- a record corresponding to the condition was found, locked (if necessary) and loaded in memory: HFound returns True.
- the data file is empty or there is no record corresponding to the condition: HOut returns True.
- the function tries to lock a record that is already locked in read-only: HErrorLock returns True and HOut returns True.
// Find the last record for which the Customer name is Moore
HSeekLast(Customer, Name, "Moore")
// This example is used to find all the customers
// whose turnover is less than a specific value.
HSeekLast(Customer, Turnover, X)
WHILE NOT HOut(Customer)
AddCustomerList()
HPrevious(Customer, Turnover)
END
Syntax
<Result> = HSeekLast(<Data file> , <Key item> , <Sought value> [, <Options>])
<Result>: Boolean
- True if the position was set on the record (corresponds to the value of HFound).
- False if a problem occurs. This problem can be caused by:
- a positioning problem (empty data file, etc.): HFound returns False and HError returns 0.
- an error: HError returns an integer other than 0. HErrorInfo returns more details.
<Data file>: Character string
Name of the HFSQL data file used.
<Key item>: Character string
Name of key item on which the search will be performed.
<Sought value>: Type corresponding to the value
Value of the sought item.
<Options>: Optional constant (or combination of constants)
Configures:- the lock mode applied to the sought record
- the type of search performed.
| |
| hGeneric | Generic search (see the Notes)
An exact-match search is performed by default (constant not specified). |
| 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 data files.
By default, the iteration performed after HSeekLast ignores the filter. |
| hLimitParsing | The iteration will stop when the last searched value is found. The current record will correspond to this last record found.
HFound will be set to False and HOut will be set to True.
This constant is used to optimize the search speed in Client/Server mode. |
| hLockNo | No lock: the record can be read or modified by another application during the reading. |
| hLockReadWrite | Lock in read/write: the record cannot be read or modified by another application.
|
| hLockWrite | Lock in write mode: the record can be read by another application but it cannot be modified by another application. |
Remarks
Generic search/Exact-match search
- Generic search (mainly on the Character String items): Finds all records starting with the specified value.
For example: When a generic search is performed on "Smith" (for the NAME item), all records whose Name item starts with "Smith" will match the search. Therefore, the record containing "Smither" will correspond to the search (HFound returns True). - Exact-match search: Finds all records that exactly correspond to the specified value.
For example: When an exact-match search is performed on "Smith" (for the NAME item), HFound returns True for the records whose item exactly matches "Smith". - Examples or searches performed on CUSTOMER file sorted by name:
| | | | | |
| Sought value | Options | HSeekLast sets the position on the record | HFound returns | HOut returns | Explanations |
| Durand | | 6 | True | False | Durand exists.
The beginning of data file was not reached yet. |
| Dupuis | | 5 | False | False | Dupuis does not exist. Positioning on the first lower value (Moore).
The beginning of data file was not reached yet. |
| Moor | hGeneric | 5 | True | False | Moor does not exist but the search is generic, and Moore is found (among others).
The beginning of data file was not reached yet. |
| Moor | | The record was not found (no move) | False | False | Moor does not exist.
The beginning of data file was not reached yet. |
| Bernard | | The record was not found (no move) | False | True | Bernard does not exist.
Positioning on the first lower value (this value does not exist): The beginning of data file was reached. |
Performing a search on a composite key
Several methods can be used to perform a search on a composite key:
Using a list of values
The following syntax is used to perform a search on a composite key:
HSeekLast(<File name>, <Name of composite key>, ...
[<Search value of first element of composite key>,
<Search value of first element of composite key>, ...])
Example:
// Find the record
HSeekLast(Customer, LastName_FirstName, ["Moore", "Vince"])
Search on an array item
The search is performed on the first array element (element with index 1). To perform a search on the other array elements, use the filters or queries.
Search and filter
If a filter is enabled (
HFilter), the search takes the filter into account.