January 2002
Intermediate to advanced
640 pages
16h 39m
English
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Begin
Starts a chained-mode transaction block.
Synopsis
BEGIN [ WORK | TRANSACTION ]
Parameters
WORK | TRANSACTIONA pair of optional noise keywords. They can be ignored, or used to make your SQL more readable.
Results
BEGINThe message returned when a transaction begins.
NOTICE: BEGIN: already a transaction in progressThe notice returned if a transaction is already in progress within your PostgreSQL session. You cannot nest multiple transactions. The transaction you have in progress is not altered when this happens.
Description
PostgreSQL executes transactions in unchained mode by default. Also called autocommit, this mode encapsulates each user statement in an implicit transaction, and automatically finalizes the transaction by either committing the modification, or performing a rollback, depending on whether or not the execution was successful.
Using BEGIN specifies that you want to enter a transaction block using
chained mode, in which statements will be queued by the database, and then sent in a single
transaction when the database receives a COMMIT command. Alternatively, the
queued statements can be discarded by a ROLLBACK, or by an unexpected
disconnection.
Chained mode can be useful when you are working with multiple related tables, and also to increase database performance in general. Executing statements in chained mode uses less CPU and disk resources, as there is only one commit needed per block of statements executed.
When a transaction is committed, the database will attempt to ...
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