What is Transaction?

Question Posted / sivasiva

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What is Transaction?..

Answer / sivasiva

A transaction in SQL (structured query language) is a
larger unit of database processing that contains one or
more database access operations like insertion ,deletion,
retrieval and modification operations.

These transaction are required to fulfil certain
characteristics and they are :

Atomicity: The transaction is either performed entirely or
not performed at all.
Isolation: The transaction should not be interfered by any
other transaction executing concurrently.
Durability: The changes made by the transaction should be
permanently committed in the database.
Consistency preservation: If the database was consistent
before the execution of the transaction .It should remain
consistent after the complete execution of that transaction.

There are two types of transactions: explicit and implicit

Explicit are those that need to be specified like : commit
and roll-back

Commit transaction signals that the transaction was
successfully executed and the changes/ updates (if any)
made by the transaction have been committed to the database
and these changes cannot be undone.

Roll-back signals that the transaction was not successfully
executed , and the changes/updates made by the transaction
have to be undone.

Implicit transactions are those that mark beginning and
end of the transaction, each statement like update,
delete , insert run within these implicit
transactions.,However, you can explicitly specify the
beginning and ending of the transaction by "begin
transaction" and "end transaction" statements respectively.
All the statements within these two boundaries will be
marked as one transaction.

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What is Transaction?..

Answer / subba reddy

A transaction is a series of SQL data manipulation
statements that does a logical unit of work. Oracle
treats the series of SQL statements as a unit so that all
the changes brought about by the statements are
either committed (made permanent) or rolled back (undone)
at the same time. If your program fails in the
middle of a transaction, the database is automatically
restored to its former state

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