doc/src/sgml/ref/start_transaction.sgml

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