Baoding-FenShuaJiang
/
Green_GoodERP18_FSJ_Standard
Obserwuj 1
Polub 0
Wiki 捐赠
gooderp18绿色标准版
Nie możesz wybrać więcej, niż 25 tematów Tematy muszą się zaczynać od litery lub cyfry, mogą zawierać myślniki ('-') i mogą mieć do 35 znaków.
Gałąź: master
Gałęzie Tagi
${ item.name }
Utwórz gałąź ${ searchTerm }
z 'master'
${ noResults }
Green_GoodERP18_FSJ_Standard/PostgreSQL/doc/postgresql/html/sql-begin.html

71 lines
7.1KB
Czysty Bezpośredni odnośnik Wina Historia 

  1. <?xml version="1.0" encoding="UTF-8" standalone="no"?>

  2. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>BEGIN</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="sql-analyze.html" title="ANALYZE" /><link rel="next" href="sql-call.html" title="CALL" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">BEGIN</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-analyze.html" title="ANALYZE">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><th width="60%" align="center">SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-call.html" title="CALL">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-BEGIN"><div class="titlepage"></div><a id="id-1.9.3.47.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">BEGIN</span></h2><p>BEGIN — start a transaction block</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">

  3. BEGIN [ WORK | TRANSACTION ] [ <em class="replaceable"><code>transaction_mode</code></em> [, ...] ]

  4. 

  5. <span class="phrase">where <em class="replaceable"><code>transaction_mode</code></em> is one of:</span>

  6. 

  7.     ISOLATION LEVEL { SERIALIZABLE | REPEATABLE READ | READ COMMITTED | READ UNCOMMITTED }

  8.     READ WRITE | READ ONLY

  9.     [ NOT ] DEFERRABLE

  10. </pre></div><div class="refsect1" id="id-1.9.3.47.5"><h2>Description</h2><p>

  11.    <code class="command">BEGIN</code> initiates a transaction block, that is,

  12.    all statements after a <code class="command">BEGIN</code> command will be

  13.    executed in a single transaction until an explicit <a class="xref" href="sql-commit.html" title="COMMIT"><span class="refentrytitle">COMMIT</span></a> or <a class="xref" href="sql-rollback.html" title="ROLLBACK"><span class="refentrytitle">ROLLBACK</span></a> is given.

  14.    By default (without <code class="command">BEGIN</code>),

  15.    <span class="productname">PostgreSQL</span> executes

  16.    transactions in <span class="quote">“<span class="quote">autocommit</span>”</span> mode, that is, each

  17.    statement is executed in its own transaction and a commit is

  18.    implicitly performed at the end of the statement (if execution was

  19.    successful, otherwise a rollback is done).

  20.   </p><p>

  21.    Statements are executed more quickly in a transaction block, because

  22.    transaction start/commit requires significant CPU and disk

  23.    activity. Execution of multiple statements inside a transaction is

  24.    also useful to ensure consistency when making several related changes:

  25.    other sessions will be unable to see the intermediate states

  26.    wherein not all the related updates have been done.

  27.   </p><p>

  28.    If the isolation level, read/write mode, or deferrable mode is specified, the new

  29.    transaction has those characteristics, as if

  30.    <a class="xref" href="sql-set-transaction.html" title="SET TRANSACTION"><span class="refentrytitle">SET TRANSACTION</span></a>

  31.    was executed.

  32.   </p></div><div class="refsect1" id="id-1.9.3.47.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">WORK</code><br /></span><span class="term"><code class="literal">TRANSACTION</code></span></dt><dd><p>

  33.       Optional key words. They have no effect.

  34.      </p></dd></dl></div><p>

  35.    Refer to <a class="xref" href="sql-set-transaction.html" title="SET TRANSACTION"><span class="refentrytitle">SET TRANSACTION</span></a> for information on the meaning

  36.    of the other parameters to this statement.

  37.   </p></div><div class="refsect1" id="id-1.9.3.47.7"><h2>Notes</h2><p>

  38.    <a class="xref" href="sql-start-transaction.html" title="START TRANSACTION"><span class="refentrytitle">START TRANSACTION</span></a> has the same functionality

  39.    as <code class="command">BEGIN</code>.

  40.   </p><p>

  41.    Use <a class="xref" href="sql-commit.html" title="COMMIT"><span class="refentrytitle">COMMIT</span></a> or

  42.    <a class="xref" href="sql-rollback.html" title="ROLLBACK"><span class="refentrytitle">ROLLBACK</span></a>

  43.    to terminate a transaction block.

  44.   </p><p>

  45.    Issuing <code class="command">BEGIN</code> when already inside a transaction block will

  46.    provoke a warning message.  The state of the transaction is not affected.

  47.    To nest transactions within a transaction block, use savepoints

  48.    (see <a class="xref" href="sql-savepoint.html" title="SAVEPOINT"><span class="refentrytitle">SAVEPOINT</span></a>).

  49.   </p><p>

  50.    For reasons of backwards compatibility, the commas between successive

  51.    <em class="replaceable"><code>transaction_modes</code></em> can be

  52.    omitted.

  53.   </p></div><div class="refsect1" id="id-1.9.3.47.8"><h2>Examples</h2><p>

  54.    To begin a transaction block:

  55. 

  56. </p><pre class="programlisting">

  57. BEGIN;

  58. </pre></div><div class="refsect1" id="id-1.9.3.47.9"><h2>Compatibility</h2><p>

  59.    <code class="command">BEGIN</code> is a <span class="productname">PostgreSQL</span>

  60.    language extension.  It is equivalent to the SQL-standard command

  61.    <a class="xref" href="sql-start-transaction.html" title="START TRANSACTION"><span class="refentrytitle">START TRANSACTION</span></a>, whose reference page

  62.    contains additional compatibility information.

  63.   </p><p>

  64.    The <code class="literal">DEFERRABLE</code>

  65.    <em class="replaceable"><code>transaction_mode</code></em>

  66.    is a <span class="productname">PostgreSQL</span> language extension.

  67.   </p><p>

  68.    Incidentally, the <code class="literal">BEGIN</code> key word is used for a

  69.    different purpose in embedded SQL. You are advised to be careful

  70.    about the transaction semantics when porting database applications.

  71.   </p></div><div class="refsect1" id="id-1.9.3.47.10"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-commit.html" title="COMMIT"><span class="refentrytitle">COMMIT</span></a>, <a class="xref" href="sql-rollback.html" title="ROLLBACK"><span class="refentrytitle">ROLLBACK</span></a>, <a class="xref" href="sql-start-transaction.html" title="START TRANSACTION"><span class="refentrytitle">START TRANSACTION</span></a>, <a class="xref" href="sql-savepoint.html" title="SAVEPOINT"><span class="refentrytitle">SAVEPOINT</span></a></span></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-analyze.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql-commands.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sql-call.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">ANALYZE </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> CALL</td></tr></table></div></body></html>
上海开阖软件有限公司 沪ICP备12045867号-1