Delete data
You can use SQL statements, either interactively or in source code, to delete one or more rows from tables that are stored in the database.
- delete method – Delete one row at a time.
- doDelete method – Delete one row at a time.
- delete_from statement – Delete multiple rows at the same time. By using the delete_from statement, you reduce communication between the application and the database. Therefore, you help increase performance. In some situations, this set-based operation can fall back to a record-by-record operation. For more information, see Conversion of operations from set-based to record-by-record.
delete method
The delete method deletes the current record from the database. To use this method, use a where clause to specify the rows to delete. One record at a time is then removed from the specified table.
The delete method can be overridden. For example, you might want to add extra validation before records are deleted. If you override the delete method, you can run the original (base) version of the delete method by calling the doDelete method. Therefore, a call to the doDelete method is equivalent to a call to super() in the delete method.
In the following example, all records in the NameValuePair table that satisfy the where clause (that is, all records where the value of the Name field equals Name1) are deleted from the database. One record is deleted at a time.
ttsBegin;
NameValuePair nameValuePair;
while select forUpdate nameValuePair
where nameValuePair.Name == 'Name1'
{
nameValuePair.delete();
}
ttsCommit;
The following example deletes records from the LedgerJournalTrans table and updates the associated number sequence.
int counter = 0;
str _journalNum = '';
str _voucher = '';
LedgerJournalTrans ledgerJournalTrans;
LedgerJournalTable ledgerJournalTable;
ttsBegin;
while select forUpdate ledgerJournalTrans
index hint NumVoucherIdx
where ledgerJournalTrans.journalNum == _journalNum
&& ledgerJournalTrans.voucher == _voucher
{
ledgerJournalTrans.doDelete();
counter++;
}
if (counter && ledgerJournalTable.journalType != LedgerJournalType::Periodic)
{
NumberSeq::release(ledgerJournalTable.voucherSeries, _voucher);
}
ttsCommit;
doDelete method
Like the delete table method, the doDelete table method deletes the current record from the database. Use the doDelete method if the delete table method has been overridden, and you want to run the original (base) version of that method instead of the overridden version. Therefore, a call to the doDelete method is equivalent to a call to super() in the delete method.
Warning
A call to doDelete skips all logic, including database event handlers (for example, onDeleting and onDeleted), chain-of-command onDelete(), and the delete() call itself. It's generally considered bad practice to use doDelete, and we don't recommend that you use it.
delete_from statement
The delete_from operator is a record set–based operator that removes multiple records at the same time. This approach can be more efficient and faster than an approach that uses the delete method in a loop to delete one record at a time. If you've overridden the delete method, the system interprets the delete_from statement into code that calls the delete method one time for each row that is deleted.
The following example deletes all records in the NameValuePair table where the value in the Name column is Name1.
NameValuePair nameValuePair;
delete_from nameValuePair where nameValuePair.Name == 'Name1';
In contrast to the previous example, the following example is inefficient, because it issues a separate SQL delete call to the database server for each record. The delete method never deletes more than one record per call.
// Example of inefficient code.
MyWidgetTable tabWidget; // extends xRecord.
ttsBegin;
while select forUpdate tabWidget
where tabWidget .quantity <= 100
{
tabWidget.delete();
}
ttsCommit;
A delete operation that has an inner join
Inner joins aren't supported on the delete_from statement. Therefore, you can't use the unmodified join keyword on the delete_from statement. However, you can logically perform an inner join by using other techniques.
The following example shows the recommended way to use the delete_from method and inner joins. This example is relatively efficient. It issues a separate delete_from statement for each loop iteration. However, each delete_from statement can delete multiple records (a subset of all the records that the job deletes).
MyWidgetTable tabWidget; // extends xRecord.
ttsBegin;
while select from tabGalaxy
where tabGalaxy .isTrusted == 0
{
delete_from tabWidget
where tabWidget .GalaxyRecId == tabGalaxy .RecId;
}
ttsCommit;
A delete operation that uses the notexists join keyword
You can use the notexists join keyword pair in a delete_from statement. The delete_from statements in the following example are efficient. The notexists join clause enables the delete_from statement to delete a specific set of rows. In this example, the delete_from statement removes all parent-order header rows that there are no child-order line rows for. You can also use the exists join clause on the delete_from statement.
static void DeleteFromNotexists3bJob(Args _args)
{
GmTabOrderHeader tabOHeader;
GmTabOrderLine tabOLine;
AddressState tabAddressState;
str 127 sOH_Info;
str 127 sOL_Data;
int64 i64OHRecId;
delete_from tabOLine;
delete_from tabOHeader;
// Inserts into parent table.
sOH_Info = "Albert needs tires.";
insert_recordset tabOHeader
(OH_Info)
select firstOnly sOH_Info from tabAddressState;
sOH_Info = "Benson wants plastic.";
insert_recordset tabOHeader
(OH_Info)
select firstOnly sOH_Info from tabAddressState;
// Obtain a OrderHeader RecId,
// use it to insert one child row.
sOL_Data = "4 re-treads.";
while select firstOnly tabOHeader
order by OH_Info
where tabOHeader .OH_Info like "A*"
{
i64OHRecId = tabOHeader .RecId;
insert_recordset tabOLine
(OL_Data ,OrderHeaderRecId)
select firstOnly
sOL_Data ,i64OHRecId
from tabAddressState;
break;
}
// Before the delete notexists.
// Display all parent, and then all child rows.
while select tabOHeader
order by OH_Info
{
info(strFmt("Before: OHeader: OH_Info==%1 , RecId==%2"
,tabOHeader .OH_Info ,tabOHeader .RecId));
}
while select tabOLine
order by OL_Data
{
info(strFmt("Before: OLine: OL_Data==%1 , OrderHeaderRecId==%2"
,tabOLine .OL_Data ,tabOLine .OrderHeaderRecId));
}
// Delete_From NotExists Join, to remove from the
// parent table all order headers without children.
delete_from tabOHeader
notexists join tabOLine
where tabOHeader .RecId ==
tabOLine .OrderHeaderRecId;
info(strFmt("%1 is the number of childless OHeader records deleted."
,tabOHeader.rowCount()));
// After the delete notexists.
// Display all parent, and then all child rows.
info("- - - - - - - - - - - - - - -");
while select tabOHeader
order by OH_Info
{
info(strFmt("After: OHeader: OH_Info==%1 , RecId==%2"
,tabOHeader .OH_Info ,tabOHeader .RecId));
}
while select tabOLine
order by OL_Data
{
info(strFmt("After: OLine: OL_Data==%1 , OrderHeaderRecId==%2"
,tabOLine .OL_Data ,tabOLine .OrderHeaderRecId));
}
/************** Actual Infolog output
Message (12:54:14 pm)
Before: OHeader: OH_Info==Albert needs tires. , RecId==5637144608
Before: OHeader: OH_Info==Benson wants plastic. , RecId==5637144609
Before: OLine: OL_Data==4 re-treads. , OrderHeaderRecId==5637144608
1 is the number of childless OHeader records deleted.
- - - - - - - - - - - - - - -
After: OHeader: OH_Info==Albert needs tires. , RecId==5637144608
After: OLine: OL_Data==4 re-treads. , OrderHeaderRecId==5637144608
**************/
}