When (2,4) is deleted. Since C is a foreign key referring A with delete on cascade, all entries with value 2 in C must be deleted. So (5, 2) and (7, 2) are deleted. As a result of this 5 and 7 are deleted from A which causes (9, 5) to be deleted.
When (2,4) is deleted. Since C is a foreign key referring A with delete on cascade, all entries with value 2 in C must be deleted. So (5, 2) and (7, 2) are deleted. As a result of this 5 and 7 are deleted from A which causes (9, 5) to be deleted.
The deferred-modification technique ensures transaction atomicity by recording all database modifications in the log, but deferring all write operations of a transaction until the transaction partially commits (i.e., once the final action of the transaction has been executed). Then the information iRead more
The deferred-modification technique ensures transaction atomicity by recording all database modifications in the log, but deferring all write operations of a transaction until the transaction partially commits (i.e., once the final action of the transaction has been executed). Then the information in the logs is used to execute the deferred writes. If the system crashes or if the transaction aborts, then the information in the logs is ignored.
The immediate-update technique allows database modifications to be output to the database while the transaction is still in the active state. These modifications are called uncommitted modifications. In the event of a crash or transaction failure, the system must use the old-value field of the log records to restore the modified data items.
Write a trigger to ensure that no employee of age less than 25 can be inserted in the database.
AGE
AGE
See lessThe following table has two attributes A and C where A is the primary key and C is the foreign …
When (2,4) is deleted. Since C is a foreign key referring A with delete on cascade, all entries with value 2 in C must be deleted. So (5, 2) and (7, 2) are deleted. As a result of this 5 and 7 are deleted from A which causes (9, 5) to be deleted.
Compare the deferred-modification and immediate-modification version of the log-based recovery schemes, in terms of ease of implementation and overhead cost
The deferred-modification technique ensures transaction atomicity by recording all database modifications in the log, but deferring all write operations of a transaction until the transaction partially commits (i.e., once the final action of the transaction has been executed). Then the information iRead more
The deferred-modification technique ensures transaction atomicity by recording all database modifications in the log, but deferring all write operations of a transaction until the transaction partially commits (i.e., once the final action of the transaction has been executed). Then the information in the logs is used to execute the deferred writes. If the system crashes or if the transaction aborts, then the information in the logs is ignored.
The immediate-update technique allows database modifications to be output to the database while the transaction is still in the active state. These modifications are called uncommitted modifications. In the event of a crash or transaction failure, the system must use the old-value field of the log records to restore the modified data items.
See lessConsider money is transferred from (1)account-A to account-B and (2) account-B to account-A. Which form a transaction will it be? …
account-A to account-B: A’s Account Open_Account(A) Old_Balance = A.balance New_Balance = Old_Balance - 500 A.balance = New_Balance Close_Account(A) B’s Account Open_Account(B) Old_Balance = B.balance New_Balance = Old_Balance + 500 B.balance = New_Balance Close_Account(B) account-B to account-A: B’Read more
Create a package with procedure that shows the usage of the WHILE loop to calculate the average of user entered …
calculate-the-average-of-user
calculate-the-average-of-user
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