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<REFENTRY ID="SQL-BEGINWORK">
<REFMETA>
<REFENTRYTITLE>
BEGIN WORK
</REFENTRYTITLE>
<REFMISCINFO>SQL - Language Statements</REFMISCINFO>
</REFMETA>
<REFNAMEDIV>
<REFNAME>
BEGIN WORK
</REFNAME>
<REFPURPOSE>
Begins a transaction
</REFPURPOSE>
<REFSYNOPSISDIV>
<REFSYNOPSISDIVINFO>
<DATE>1998-09-08</DATE>
</REFSYNOPSISDIVINFO>
<SYNOPSIS>
BEGIN [ WORK | TRANSACTION ]
</SYNOPSIS>
<REFSECT2 ID="R2-SQL-BEGINWORK-1">
<REFSECT2INFO>
<DATE>1998-09-08</DATE>
</REFSECT2INFO>
<TITLE>
Inputs
</TITLE>
<PARA>
None
</REFSECT2>
<REFSECT2 ID="R2-SQL-BEGINWORK-2">
<REFSECT2INFO>
<DATE>1998-09-08</DATE>
</REFSECT2INFO>
<TITLE>
Outputs
</TITLE>
<PARA>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<returnvalue>BEGIN</returnvalue>
</TERM>
<LISTITEM>
<PARA>
This signifies that a new transaction has been started.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<returnvalue>NOTICE: BeginTransactionBlock and not in default state</returnvalue>
</TERM>
<LISTITEM>
<PARA>
This indicates that a transaction was already in progress.
The current transaction is not affected.
</VARIABLELIST>
</REFSECT2>
</REFSYNOPSISDIV>
<REFSECT1 ID="R1-SQL-BEGINWORK-1">
<REFSECT1INFO>
<DATE>1998-09-08</DATE>
</REFSECT1INFO>
<TITLE>
Description
</TITLE>
<para>
<command>BEGIN</command> initiates a user transaction
which <productname>Postgres</productname> will
guarantee is serializable with respect to all concurrently
executing transactions. <productname>Postgres</productname> uses two-phase
locking
to perform this task. If the transaction is committed,
<productname>Postgres</productname> will ensure either that all updates are
done or else
that none of
them are done. Transactions have the standard ACID
(atomic, consistent, isolatable, and durable) property.
</para>
<REFSECT2 ID="R2-SQL-BEGINWORK-3">
<REFSECT2INFO>
<DATE>1998-09-08</DATE>
</REFSECT2INFO>
<TITLE>
Notes
</TITLE>
<PARA>
The keyword TRANSACTION is just a cosmetic alternative to WORK.
Neither keyword need be specified.
</PARA>
<PARA>
Refer to the <command>LOCK</command> statement for further information
about locking tables inside a transaction.
</PARA>
<PARA>
Use <command>COMMIT</command> or <command>ROLLBACK</command>
to terminate a transaction.
</PARA>
</REFSECT2>
<REFSECT1 ID="R1-SQL-BEGINWORK-2">
<TITLE>
Usage
</TITLE>
<PARA>To begin a user transaction:
<ProgramListing>
BEGIN WORK;
</ProgramListing>
</REFSECT1>
<REFSECT1 ID="R1-SQL-BEGINWORK-3">
<TITLE>
Compatibility
</TITLE>
<PARA>
<command>BEGIN</command>
is a <productname>Postgres</productname> language extension.
<REFSECT2 ID="R2-SQL-BEGINWORK-4">
<REFSECT2INFO>
<DATE>1998-09-08</DATE>
</REFSECT2INFO>
<TITLE>
SQL92
</TITLE>
<PARA>
There is no explicit BEGIN WORK command in <acronym>SQL92</acronym>;
transaction initiation
is always implicit and it terminates either with a COMMIT or with
a ROLLBACK statement.
</PARA>
</refsect2>
</refsect1>
</REFENTRY>
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