SQL BEGIN TRANSACTION

SQL BEGIN TRANSACTION is a SQL statement used to start a new transaction in a database.

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1. Overview

SQL BEGIN TRANSACTION marks the beginning of a new transaction in a database. A transaction is a sequence of one or more SQL statements that are executed as a single unit of work. By starting a transaction, you can group multiple SQL statements together and ensure that they are executed atomically, i.e., either all the statements are executed successfully, or none of them are.

Transactions are used to maintain the consistency and integrity of data in a database, especially in multi-user environments where multiple transactions may be executed concurrently.

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2. Syntax

The syntax for SQL BEGIN TRANSACTION varies slightly depending on the database system being used. In most relational database management systems (RDBMS), such as MySQL, PostgreSQL, and SQL Server, the syntax is as follows:

BEGIN TRANSACTION;

This statement starts a new transaction in the current session. Any subsequent SQL statements executed after SQL BEGIN TRANSACTION will be part of the same transaction until it is explicitly committed or rolled back.

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3. Example

Consider a scenario where you need to transfer funds from one bank account to another while ensuring that the transaction is executed atomically. You can use SQL BEGIN TRANSACTION to start a new transaction and group the update statements together:

Example:

-- Start a new transaction
BEGIN TRANSACTION;

-- Update the balance of the source account
UPDATE accounts SET balance = balance - 100 WHERE account_id = 'source';

-- Update the balance of the destination account
UPDATE accounts SET balance = balance + 100 WHERE account_id = 'destination';

-- Commit the transaction
COMMIT;

In this example, the SQL BEGIN TRANSACTION statement marks the beginning of a transaction. The subsequent update statements are executed as part of the same transaction, ensuring that the funds transfer operation is atomic.

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4. Conclusion

SQL BEGIN TRANSACTION is a fundamental SQL statement used to start a new transaction in a database. By grouping SQL statements together within a transaction, you can ensure atomicity and maintain the integrity and consistency of data in the database.