<Source>.Delete (Function)

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Managing databases

HFSQL functions

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Delete

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<Source>.Delete (Function)

In french: <Source>.Supprime

Not available with this kind of connection

Deletes a record from a data file (query or view). The record is deleted logically and physically. It cannot be restored (unlike the records crossed by <Source>.Cross).

The following operations are performed:

the record is deleted: the record is inactive and it is not referenced in the index anymore. The data is not kept.
the indexes (corresponding to the record keys) are deleted from the index file.
the memos associated with the record are deleted from the memo file.

After running <Source>.Delete, the record is inserted in the list of deleted records and will be reused by <Source>.Add.

The deleted record is no longer visible in the iteration on the current item. This record will no longer be visible in iterations on other items if these iterations are reinitialized.

WINDEV, WINDEV Mobile and WEBDEV propose an automatic management of errors for the following types of errors: Duplicate error, integrity error, password error, modification conflict error and status error during modification conflict, lock error. For more details, see Assisted HFSQL error handling.

Remark: To delete all records from a data file, use <Source>.DeleteAll.

Example

// Deletes the record #123
Customer.Delete(123)

// Delete the customer orders
Order.ReadSeekFirst(CustNum, ValCustNum)
WHILE Order.Found() = True
Order.Delete()
Order.ReadNext()
END

// Delete the customer orders
FOR EACH Order where CustNum = CustNumVal
Order.Delete()
END

Syntax

<Result> = <Source>.Delete([<Record number> [, <Options>]])

<Result>: Boolean

True if the record was deleted,
False if a problem occurred (locked record, etc. (see the special cases)). HErrorInfo is used to identify the error.
If the record to delete is already deleted, <Source>.Delete returns True.

<Source>: Type corresponding to the specified source

Name of HFSQL data file or view used.

<Record number>: Optional integer

Number of the record to delete. If this parameter is not specified (if it is equal to 0 or to the hCurrentRecNum constant), the current record will be deleted. However, the current record will remain the deleted record.

CAUTION: Do not confuse the record number with the automatic identifier associated with the record.
In most cases, these two numbers are not identical. The record number is returned by <Source>.RecNum.
This parameter must correspond to the current record number (hCurrentRecNum constant).
Access by JDBC: This parameter must correspond to the current record number (hCurrentRecNum constant).

<Options>: Optional constant

Configures the integrity management performed on the deleted record.
hIgnoreIntegrity Ignores the integrity check for this operation, even if the automatic integrity check is enabled (<Connection variable>.SetIntegrity)
This parameter is ignored.
Access by JDBC: This parameter is ignored.

Remarks

Handling a deleted record

A deleted record will not be read:
- by iteration functions: <Source>.First, <Source>.Last, <Source>.Next, <Source>.Previous, <Source>.ReadFirst, <Source>.ReadLast, <Source>.ReadNext, <Source>.ReadPrevious, <Source>.Forward, <Source>.Backward.
- by the search functions: <Source>.SeekFirst, <Source>.ReadSeekFirst, <Source>.SeekLast, <Source>.ReadSeekLast.
A deleted record can be read by <Source>.Read. Its content will be incomplete or inconsistent.
The physical location of a deleted record can be immediately re-used by <Source>.Add for example.

Number of deleted records

<Source>.NbRec is used to find out the number of records deleted from the data file.

Remark: For backward compatibility with Hyper File 5.5, the H.NbDel variable can also be used to find out the number of deleted records.

Deleting a record from a query

Deleting a record from a query can be performed:

in the query result
in the data files handled by the query (hModifyFile constant used in <Source>.ExecuteQuery or <Source>.ExecuteSQLQuery). In this case, the hWithFilter constant is automatically selected.

Regardless of the query execution mode (with or without the hWithFilter constant), <Source>.Delete can only be used on single-file queries.

Caution:

On data files not in HFSQL format, there is no need to specify the hModifyFile constant in <Source>.ExecuteQuery or <Source>.ExecuteSQLQuery: the data files taking part in the query are automatically modified when modifying the query result.
Records cannot be deleted from a query that uses groups or aggregates.
The management of integrity and duplicates is not performed during the operations on the multi-file queries: it is recommended to use transactions to avoid any problems.

For more details, see Modifying the query content.

Version of data file

If <Source>.Delete is successful, the data file version number is modified. This version number is returned by <Source>.Version.

Size of the data file

The deletion of one or more records has no incidence on the total file size on disk. The locations left empty in the data files by the deletions will be re-used during the next additions of records (<Source>.Add). This feature is used to get better performance, the reduction of file size being costly in time.

However, if after many deletions it is necessary to reduce the size of a data file, it can be reindexed (via <Source>.Index, WDMap or the HFSQL Control Center).

Deletion and lock

If a lock problem occurs when "deleting" a record (attempt to delete a record locked in write mode for example), the record is not deleted and HErrorLock returns True.

xBase/FoxFro

<Source>.Delete and <Source>.Cross have the same effect: the record is crossed but it is not deleted. Therefore, the record can be re-enabled using <Source>.Modify. In this case, <Source>.State returns the hStateCrossed constant for a deleted record (instead of hStateDel).

To physically delete the crossed records, you must use <Source>.Index.

FoxPro files: <Source>.Index is not available

Component: wd280hf.dll