doc/src/sgml/ref/start_transaction.sgml

   1 <!--
   2 doc/src/sgml/ref/start_transaction.sgml
   3 PostgreSQL documentation
   4 -->
   5
   6 <refentry id="sql-start-transaction">
   7  <indexterm zone="sql-start-transaction">
   8   <primary>START TRANSACTION</primary>
   9  </indexterm>
  10
  11  <refmeta>
  12   <refentrytitle>START TRANSACTION</refentrytitle>
  13   <manvolnum>7</manvolnum>
  14   <refmiscinfo>SQL - Language Statements</refmiscinfo>
  15  </refmeta>
  16
  17  <refnamediv>
  18   <refname>START TRANSACTION</refname>
  19   <refpurpose>start a transaction block</refpurpose>
  20  </refnamediv>
  21
  22  <refsynopsisdiv>
  23 <synopsis>
  24 START TRANSACTION [ <replaceable class="parameter">transaction_mode</replaceable> [, ...] ]
  25
  26 <phrase>where <replaceable class="parameter">transaction_mode</replaceable> is one of:</phrase>
  27
  28     ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED }
  29     READ WRITE | READ ONLY
  30     [ NOT ] DEFERRABLE
  31 </synopsis>
  32  </refsynopsisdiv>
  33
  34  <refsect1>
  35   <title>Description</title>
  36
  37   <para>
  38    This command begins a new transaction block. If the isolation level,
  39    read/write mode, or deferrable mode is specified, the new transaction has those
  40    characteristics, as if <link linkend="sql-set-transaction"><command>SET TRANSACTION</command></link> was executed. This is the same
  41    as the <link linkend="sql-begin"><command>BEGIN</command></link> command.
  42   </para>
  43  </refsect1>
  44
  45  <refsect1>
  46   <title>Parameters</title>
  47
  48   <para>
  49    Refer to <xref linkend="sql-set-transaction"/> for information on the meaning
  50    of the parameters to this statement.
  51   </para>
  52  </refsect1>
  53
  54  <refsect1>
  55   <title>Compatibility</title>
  56
  57   <para>
  58    In the standard, it is not necessary to issue <command>START TRANSACTION</command>
  59    to start a transaction block: any SQL command implicitly begins a block.
  60    <productname>PostgreSQL</productname>'s behavior can be seen as implicitly
  61    issuing a <command>COMMIT</command> after each command that does not
  62    follow <command>START TRANSACTION</command> (or <command>BEGIN</command>),
  63    and it is therefore often called <quote>autocommit</quote>.
  64    Other relational database systems might offer an autocommit feature
  65    as a convenience.
  66   </para>
  67
  68   <para>
  69    The <literal>DEFERRABLE</literal>
  70    <replaceable class="parameter">transaction_mode</replaceable>
  71    is a <productname>PostgreSQL</productname> language extension.
  72   </para>
  73
  74   <para>
  75    The SQL standard requires commas between successive <replaceable
  76    class="parameter">transaction_modes</replaceable>, but for historical
  77    reasons <productname>PostgreSQL</productname> allows the commas to be
  78    omitted.
  79   </para>
  80
  81   <para>
  82    See also the compatibility section of <xref linkend="sql-set-transaction"/>.
  83   </para>
  84  </refsect1>
  85
  86  <refsect1>
  87   <title>See Also</title>
  88
  89   <simplelist type="inline">
  90    <member><xref linkend="sql-begin"/></member>
  91    <member><xref linkend="sql-commit"/></member>
  92    <member><xref linkend="sql-rollback"/></member>
  93    <member><xref linkend="sql-savepoint"/></member>
  94    <member><xref linkend="sql-set-transaction"/></member>
  95   </simplelist>
  96  </refsect1>
  97 </refentry>