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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML
><HEAD
><TITLE
> BEGIN WORK
</TITLE
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><HR
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><H1
>BEGIN WORK</H1
><DIV
CLASS="REFNAMEDIV"
><H2
>Name</H2
> BEGIN WORK
— Begins a transaction
</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><PRE
CLASS="SYNOPSIS"
>
BEGIN [ WORK | TRANSACTION ]
</PRE
><DIV
CLASS="REFSECT2"
><H3
> Inputs
</H3
><P
> None
</P
></DIV
><DIV
CLASS="REFSECT2"
><H3
> Outputs
</H3
><P
> <P
></P
></P><DL
><DT
><SPAN
CLASS="RETURNVALUE"
>BEGIN</SPAN
></DT
><DD
><P
> This signifies that a new transaction has been started.
</P
></DD
><DT
><SPAN
CLASS="RETURNVALUE"
>NOTICE: BeginTransactionBlock and not in default state</SPAN
></DT
><DD
><P
> This indicates that a transaction was already in progress.
The current transaction is not affected.
</P
></DD
></DL
><P>
</P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><H2
> Description
</H2
><P
> <B
CLASS="COMMAND"
>BEGIN</B
> initiates a user transaction
which <SPAN
CLASS="PRODUCTNAME"
>Postgres</SPAN
> will
guarantee is serializable with respect to all concurrently
executing transactions. <SPAN
CLASS="PRODUCTNAME"
>Postgres</SPAN
> uses two-phase
locking
to perform this task. If the transaction is committed,
<SPAN
CLASS="PRODUCTNAME"
>Postgres</SPAN
> 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.
</P
><DIV
CLASS="REFSECT2"
><H3
> Notes
</H3
><P
> The keyword TRANSACTION is just a cosmetic alternative to WORK.
Neither keyword need be specified.
</P
><P
> Refer to the <B
CLASS="COMMAND"
>LOCK</B
> statement for further information
about locking tables inside a transaction.
</P
><P
> Use <B
CLASS="COMMAND"
>COMMIT</B
> or <B
CLASS="COMMAND"
>ROLLBACK</B
>
to terminate a transaction.
</P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><H2
> Usage
</H2
><P
>To begin a user transaction:
<PRE
CLASS="PROGRAMLISTING"
>BEGIN WORK;
</PRE
>
</P
></DIV
><DIV
CLASS="REFSECT1"
><H2
> Compatibility
</H2
><P
> <B
CLASS="COMMAND"
>BEGIN</B
>
is a <SPAN
CLASS="PRODUCTNAME"
>Postgres</SPAN
> language extension.
</P
><DIV
CLASS="REFSECT2"
><H3
> SQL92
</H3
><P
>
There is no explicit BEGIN WORK command in <SPAN
CLASS="ACRONYM"
>SQL92</SPAN
>;
transaction initiation
is always implicit and it terminates either with a COMMIT or with
a ROLLBACK statement.
</P
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