TCL Overview
Transaction Control Language (TCL) commands are used to manage transactions in a database. Transactions are sequences of one or more SQL statements that are executed as a single unit of work. TCL commands help maintain the integrity of data and ensure that database operations are performed reliably.
List of TCL Commands
| Command | Description |
|---|---|
COMMIT | Saves all changes made by the current transaction to the database. |
ROLLBACK | Undoes all changes made by the current transaction. |
SAVEPOINT | Sets a point within a transaction to which a rollback can be performed. |
SET TRANSACTION | Sets the properties of a transaction, such as isolation level. |
BEGIN TRANSACTION | Starts a new transaction explicitly. |
END TRANSACTION | Ends the current transaction explicitly. |
What is a Transaction?
A transaction is a sequence of SQL statements that are treated as a single unit. Transactions are used to ensure the consistency and integrity of the database by making changes only when all operations in the transaction are successful.
Characteristics of Transactions
- Atomicity: Ensures that all operations in a transaction are completed; if not, the transaction is rolled back.
- Consistency: Ensures that the database remains in a consistent state after the transaction.
- Isolation: Ensures that concurrent transactions do not interfere with each other.
- Durability: Ensures that the results of a committed transaction are permanent.