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SQL refers to Structured Query Language, a kind of language used to access, update and manipulate database. In SQL, ROLLBACK is a command that causes all data changes since the last START TRANSACTION or BEGIN to be discarded by the relational database management systems (RDBMS), so that the state of the data is "rolled back" to the way it was before those changes were made.
The valid time and transaction time do not have to be the same for a single fact. For example, consider a temporal database storing data about the 18th century. The valid time of these facts is somewhere between 1701 and 1800. The transaction time would show when the facts were inserted into the database (for example 1998-01-21).
Issuing the commands ROLLBACK or COMMIT will also discard any savepoints created since the start of the main transaction. Savepoints are defined in the SQL standard and are supported by all established SQL relational databases, including PostgreSQL , Oracle Database , Microsoft SQL Server , MySQL , IBM Db2 , SQLite (since 3.6.8), Firebird , H2 ...
The time when a transaction is valid can be called the transaction time-period. It is a technical timeline controlled by a integration layer (for example a data warehouse ). [ 1 ] More formally, it is the point-in-time during which a fact stored in the database is considered to be true.
In the fields of databases and transaction processing (transaction management), a schedule (or history) of a system is an abstract model to describe the order of executions in a set of transactions running in the system. Often it is a list of operations (actions) ordered by time, performed by a set of transactions that are executed together in ...
This includes transactions that completed after this transaction's start time, and optionally, transactions that are still active at validation time. Commit/Rollback: If there is no conflict, make all changes take effect. If there is a conflict, resolve it, typically by aborting the transaction, although other resolution schemes are possible.
A database transaction symbolizes a unit of work, performed within a database management system (or similar system) against a database, that is treated in a coherent and reliable way independent of other transactions. A transaction generally represents any change in a database. Transactions in a database environment have two main purposes:
Nonetheless, in systems such as Microsoft SQL Server, as well as connection technologies such as ODBC and Microsoft OLE DB, autocommit mode is the default for all statements that change data, in order to ensure that individual statements will conform to the ACID (atomicity-consistency-isolation-durability) properties of transactions. [1]