<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>BEGIN</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REV="MADE"
HREF="mailto:pgsql-docs@postgresql.org"><LINK
REL="HOME"
TITLE="PostgreSQL 8.4.20 Documentation"
HREF="index.html"><LINK
REL="UP"
TITLE="SQL Commands"
HREF="sql-commands.html"><LINK
REL="PREVIOUS"
TITLE="ANALYZE"
HREF="sql-analyze.html"><LINK
REL="NEXT"
TITLE="CHECKPOINT"
HREF="sql-checkpoint.html"><LINK
REL="STYLESHEET"
TYPE="text/css"
HREF="stylesheet.css"><META
HTTP-EQUIV="Content-Type"
CONTENT="text/html; charset=ISO-8859-1"><META
NAME="creation"
CONTENT="2014-02-17T20:05:31"></HEAD
><BODY
CLASS="REFENTRY"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="5"
ALIGN="center"
VALIGN="bottom"
>PostgreSQL 8.4.20 Documentation</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
HREF="sql-analyze.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="top"
><A
HREF="sql-analyze.html"
>Fast Backward</A
></TD
><TD
WIDTH="60%"
ALIGN="center"
VALIGN="bottom"
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="top"
><A
HREF="sql-checkpoint.html"
>Fast Forward</A
></TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="top"
><A
HREF="sql-checkpoint.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><H1
><A
NAME="SQL-BEGIN"
></A
>BEGIN</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN55085"
></A
><H2
>Name</H2
>BEGIN -- start a transaction block</DIV
><A
NAME="AEN55088"
></A
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN55090"
></A
><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
>BEGIN [ WORK | TRANSACTION ] [ <TT
CLASS="REPLACEABLE"
><I
>transaction_mode</I
></TT
> [, ...] ]
where <TT
CLASS="REPLACEABLE"
><I
>transaction_mode</I
></TT
> is one of:
ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED }
READ WRITE | READ ONLY</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55094"
></A
><H2
>Description</H2
><P
> <TT
CLASS="COMMAND"
>BEGIN</TT
> initiates a transaction block, that is,
all statements after a <TT
CLASS="COMMAND"
>BEGIN</TT
> command will be
executed in a single transaction until an explicit <A
HREF="sql-commit.html"
><I
>COMMIT</I
></A
> or <A
HREF="sql-rollback.html"
><I
>ROLLBACK</I
></A
> is given.
By default (without <TT
CLASS="COMMAND"
>BEGIN</TT
>),
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> executes
transactions in <SPAN
CLASS="QUOTE"
>"autocommit"</SPAN
> mode, that is, each
statement is executed in its own transaction and a commit is
implicitly performed at the end of the statement (if execution was
successful, otherwise a rollback is done).
</P
><P
> Statements are executed more quickly in a transaction block, because
transaction start/commit requires significant CPU and disk
activity. Execution of multiple statements inside a transaction is
also useful to ensure consistency when making several related changes:
other sessions will be unable to see the intermediate states
wherein not all the related updates have been done.
</P
><P
> If the isolation level or read/write mode is specified, the new
transaction has those characteristics, as if
<A
HREF="sql-set-transaction.html"
><I
>SET TRANSACTION</I
></A
>
was executed.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55107"
></A
><H2
>Parameters</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="LITERAL"
>WORK</TT
><BR><TT
CLASS="LITERAL"
>TRANSACTION</TT
></DT
><DD
><P
> Optional key words. They have no effect.
</P
></DD
></DL
></DIV
><P
> Refer to <A
HREF="sql-set-transaction.html"
><I
>SET TRANSACTION</I
></A
> for information on the meaning
of the other parameters to this statement.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55119"
></A
><H2
>Notes</H2
><P
> <A
HREF="sql-start-transaction.html"
><I
>START TRANSACTION</I
></A
> has the same functionality
as <TT
CLASS="COMMAND"
>BEGIN</TT
>.
</P
><P
> Use <A
HREF="sql-commit.html"
><I
>COMMIT</I
></A
> or
<A
HREF="sql-rollback.html"
><I
>ROLLBACK</I
></A
>
to terminate a transaction block.
</P
><P
> Issuing <TT
CLASS="COMMAND"
>BEGIN</TT
> when already inside a transaction block will
provoke a warning message. The state of the transaction is not affected.
To nest transactions within a transaction block, use savepoints
(see <A
HREF="sql-savepoint.html"
><I
>SAVEPOINT</I
></A
>).
</P
><P
> For reasons of backwards compatibility, the commas between successive
<TT
CLASS="REPLACEABLE"
><I
>transaction_modes</I
></TT
> can be
omitted.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55132"
></A
><H2
>Examples</H2
><P
> To begin a transaction block:
</P><PRE
CLASS="PROGRAMLISTING"
>BEGIN;</PRE
><P>
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55136"
></A
><H2
>Compatibility</H2
><P
> <TT
CLASS="COMMAND"
>BEGIN</TT
> is a <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>
language extension. It is equivalent to the SQL-standard command
<A
HREF="sql-start-transaction.html"
><I
>START TRANSACTION</I
></A
>, whose reference page
contains additional compatibility information.
</P
><P
> Incidentally, the <TT
CLASS="LITERAL"
>BEGIN</TT
> key word is used for a
different purpose in embedded SQL. You are advised to be careful
about the transaction semantics when porting database applications.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN55144"
></A
><H2
>See Also</H2
><A
HREF="sql-commit.html"
><I
>COMMIT</I
></A
>, <A
HREF="sql-rollback.html"
><I
>ROLLBACK</I
></A
>, <A
HREF="sql-start-transaction.html"
><I
>START TRANSACTION</I
></A
>, <A
HREF="sql-savepoint.html"
><I
>SAVEPOINT</I
></A
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="sql-analyze.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="sql-checkpoint.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>ANALYZE</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="sql-commands.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>CHECKPOINT</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
y~or5J ={Eeu磝Qk ᯘG{?+]ן?wM3X^歌>{7پK>on\jy R g/=fOroNVv~Y+ NGuÝHWyw[eQʨSb> >}Gmx[o[<{Ϯ_qF vM IENDB`
