Even if an SQL statement is executed successfully, unless the transaction containing the statement is committed, it can be rolled back and all changes made by the statement(s) can be undone. A transaction starts when one of the following events take place − INSERT INTO CUSTOMERS (ID, NAME, AGE, ADDRESS, SALARY) VALUES (1, 'Ramesh', 32, 'Ahmedabad', 2000.00 ); INSERT INTO CUSTOMERS (ID, NAME, AGE, ADDRESS, SALARY) VALUES (2, 'Khilan', 25, 'Delhi', 1500.00 ); INSERT INTO CUSTOMERS (ID, NAME, AGE, ADDRESS, SALARY) VALUES (3, 'kaushik', 23, 'Kota', 2000.00 ); INSERT INTO CUSTOMERS (ID, NAME, AGE, ADDRESS, SALARY) VALUES (4, 'Chaitali', 25, 'Mumbai', 6500.00 ); INSERT INTO CUSTOMERS (ID, NAME, AGE, ADDRESS, SALARY) VALUES (5, 'Hardik', 27, 'Bhopal', 8500.00 ); INSERT INTO CUSTOMERS (ID, NAME, AGE, ADDRESS, SALARY) VALUES (6, 'Komal', 22, 'MP', 4500.00 ); COMMIT; When a transaction is aborted due to some unprecedented situation, like system failure, the entire transaction since a commit is automatically rolled back.
If you are not using savepoint, then simply use the following statement to rollback all the changes − Savepoints are sort of markers that help in splitting a long transaction into smaller units by setting some checkpoints.
By setting savepoints within a long transaction, you can roll back to a checkpoint if required. The general syntax for the SAVEPOINT command is − INSERT INTO CUSTOMERS (ID, NAME, AGE, ADDRESS, SALARY) VALUES (7, 'Rajnish', 27, 'HP', 9500.00 ); INSERT INTO CUSTOMERS (ID, NAME, AGE, ADDRESS, SALARY) VALUES (8, 'Riddhi', 21, 'WB', 4500.00 ); SAVEPOINT sav1; UPDATE CUSTOMERS SET SALARY = SALARY 1000; ROLLBACK TO sav1; UPDATE CUSTOMERS SET SALARY = SALARY 1000 WHERE ID = 7; UPDATE CUSTOMERS SET SALARY = SALARY 1000 WHERE ID = 8; COMMIT; ROLLBACK TO sav1 − This statement rolls back all the changes up to the point, where you had marked savepoint sav1.
After that, the new changes that you make will start.
The default settings are fine for a small result set if no updating is done, but a dynamic cursor is preferred for a large result set in which the user is likely to find an answer before retrieving many of the rows.
If the data that is to be retrieved will be consumed all at once, and there is no need for positioned updates or scrolling, default result sets are recommended.
Operations subsequently performed using that WT_SESSION handle, including operations on any cursors open in that WT_SESSION handle (whether opened before or after the WT_SESSION::begin_transaction call), are part of the transaction and their effects committed by calling WT_SESSION::commit_transaction, or discarded by calling WT_SESSION::rollback_transaction.
If an implicit transaction successfully commits, the cursors in the WT_SESSION remain positioned.Further, writes do not block writes, although concurrent transactions updating the same value will fail with WT_ROLLBACK.Some applications may benefit from application-level synchronization to avoid repeated attempts to rollback and update the same value.It is called atomic because the database modifications brought about by the SQL statements that constitute a transaction can collectively be either committed, i.e., made permanent to the database or rolled back (undone) from the database.A successfully executed SQL statement and a committed transaction are not same.For more information, see Specifies one or more table hints that are allowed for a target table. If 'N' is not specified, SQL Server converts the string to the code page that corresponds to the default collation of the database or column.