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What is transaction (Transaction)

A program execution unit (unit) that accesses and may update various data items in a database

That is, it consists of multiple sql statements, which must be executed as a whole. These sql statements are submitted to the system as a whole, either all or none of them are executed.

Why do you need transactions?

For example, borrowing money:

Assuming that money is transferred from A to B, it takes at least two steps:

The funds of An are reduced.

Then B's funds increase accordingly.

Syntax steps:

Start transaction: BEGIN TRANSACTION

Transaction commit: COMMIT TRANSACTION

Transaction rollback: ROLLBACK TRANSACTION

Determine whether an error occurs in the execution of a statement:

Global variable @ @ ERROR

@ @ ERROR can only judge whether there is an error in the execution of the current T-SQL statement

To determine whether there are any errors in all T-SQL statements in the transaction, we need to accumulate the errors

Example: SET @ errorSum=@errorSum+@@error

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