?? lang_transaction.html
字號:
<html dir="LTR" xmlns="http://www.w3.org/1999/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:MSHelp="http://msdn.microsoft.com/mshelp" xmlns:tool="http://www.microsoft.com/tooltip" xmlns:ndoc="urn:ndoc-preprocess">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=Windows-1252" />
<title>TRANSACTIONS</title>
<link rel="stylesheet" type="text/css" href="ndoc.css"> </link>
<link rel="stylesheet" type="text/css" href="user.css"> </link>
<script type="text/javascript" src="ndoc.js"> </script>
</head>
<body style="display: none;">
<input type="hidden" id="userDataCache" class="userDataStyle" />
<input type="hidden" id="hiddenScrollOffset" />
<img id="dropDownImage" style="display:none; height:0; width:0;" src="drpdown.gif" />
<img id="dropDownHoverImage" style="display:none; height:0; width:0;" src="drpdown_orange.gif" />
<img id="collapseImage" style="display:none; height:0; width:0;" src="collapse.gif" />
<img id="expandImage" style="display:none; height:0; width:0;" src="exp.gif" />
<img id="collapseAllImage" style="display:none; height:0; width:0;" src="collall.gif" />
<img id="expandAllImage" style="display:none; height:0; width:0;" src="expall.gif" />
<img id="copyImage" style="display:none; height:0; width:0;" src="copycode.gif" />
<img id="copyHoverImage" style="display:none; height:0; width:0;" src="copycodeHighlight.gif" />
<div id="header">
<table width="100%" id="topTable">
<tr id="headerTableRow1">
<td align="left">
<span id="runningHeaderText">BEGIN TRANSACTION</span> </td>
</tr>
<tr id="headerTableRow2">
<td align="left">
<span id="nsrTitle">SQLite Language Reference Documentation</span>
</td>
</tr>
<tr id="headerTableRow3" style="display:none">
<td>
<a id="seeAlsoSectionLink" href="#seeAlsoToggle" onclick="OpenSection(seeAlsoToggle)">See Also</a>
<a id="exampleSectionLink" href="#codeExampleToggle" onclick="OpenSection(codeExampleToggle)">Example</a>
</td>
</tr>
</table>
<table width="100%" id="bottomTable" cellspacing="0" cellpadding="0" style="display:none">
<tr>
<td>
<span onclick="ExpandCollapseAll(toggleAllImage)" style="cursor:default;" onkeypress="ExpandCollapseAll_CheckKey(toggleAllImage)" tabindex="0">
<img ID="toggleAllImage" class="toggleAll" src="collall.gif" />
<label id="collapseAllLabel" for="toggleAllImage" style="display: none;">
Collapse All
</label>
<label id="expandAllLabel" for="toggleAllImage" style="display: none;">
Expand All
</label>
</span>
</td>
</tr>
</table>
</div>
<div id="mainSection">
<div id="mainBody">
<h1 class="heading">
SQL As Understood By SQLite</h1>
<h4>
BEGIN TRANSACTION</h4>
<p>
<table cellpadding="10">
<tr>
<td align="right" width="1%" nowrap>
<i><font color="#ff3434">sql-statement</font></i> ::=</td>
<td>
<b><font color="#2c2cf0">BEGIN </font></b>[<b><font color="#2c2cf0"> DEFERRED </font>
</b><big>|</big><b><font color="#2c2cf0"> IMMEDIATE </font></b><big>|</big><b><font
color="#2c2cf0"> EXCLUSIVE </font></b>]<b><font color="#2c2cf0"> </font></b>[<b><font
color="#2c2cf0">TRANSACTION </font></b>[<b><font color="#2c2cf0"></font></b><i><font
color="#ff3434">name</font></i><b><font color="#2c2cf0"></font></b>]<b><font color="#2c2cf0"></font></b>]<b><font
color="#2c2cf0"></font></b></td>
</tr>
</table>
<table cellpadding="10">
<tr>
<td align="right" width="1%" nowrap>
<i><font color="#ff3434">sql-statement</font></i> ::=</td>
<td>
<b><font color="#2c2cf0">END </font></b>[<b><font color="#2c2cf0">TRANSACTION </font>
</b>[<b><font color="#2c2cf0"></font></b><i><font color="#ff3434">name</font></i><b><font
color="#2c2cf0"></font></b>]<b><font color="#2c2cf0"></font></b>]<b><font color="#2c2cf0"></font></b></td>
</tr>
</table>
<table cellpadding="10">
<tr>
<td align="right" width="1%" nowrap>
<i><font color="#ff3434">sql-statement</font></i> ::=</td>
<td>
<b><font color="#2c2cf0">COMMIT </font></b>[<b><font color="#2c2cf0">TRANSACTION </font>
</b>[<b><font color="#2c2cf0"></font></b><i><font color="#ff3434">name</font></i><b><font
color="#2c2cf0"></font></b>]<b><font color="#2c2cf0"></font></b>]<b><font color="#2c2cf0"></font></b></td>
</tr>
</table>
<table cellpadding="10">
<tr>
<td align="right" width="1%" nowrap>
<i><font color="#ff3434">sql-statement</font></i> ::=</td>
<td>
<b><font color="#2c2cf0">ROLLBACK </font></b>[<b><font color="#2c2cf0">TRANSACTION
</font></b>[<b><font color="#2c2cf0"></font></b><i><font color="#ff3434">name</font></i><b><font
color="#2c2cf0"></font></b>]<b><font color="#2c2cf0"></font></b>]<b><font color="#2c2cf0"></font></b></td>
</tr>
</table>
</p>
<p>
Beginning in version 2.0, SQLite supports transactions with rollback and atomic
commit.</p>
<p>
The optional transaction name is ignored. SQLite currently does not allow nested
transactions.</p>
<p>
No changes can be made to the database except within a transaction. Any command
that changes the database (basically, any SQL command
other than SELECT) will automatically start a transaction if one is not already in effect. Automatically started transactions
are committed at the conclusion of the command.
</p>
<p>
Transactions can be started manually using the BEGIN command. Such transactions
usually persist until the next COMMIT or ROLLBACK command. But a transaction will
also ROLLBACK if the database is closed or if an error occurs and the ROLLBACK conflict
resolution algorithm is specified. See the documentation on the <a href="lang_conflict.html">
ON CONFLICT</a> clause for additional information about the ROLLBACK conflict
resolution algorithm.
</p>
<p>
In SQLite version 3.0.8 and later, transactions can be deferred, immediate, or exclusive.
Deferred means that no locks are acquired on the database until the database is
first accessed. Thus with a deferred transaction, the BEGIN statement itself does
nothing. Locks are not acquired until the first read or write operation. The first
read operation against a database creates a SHARED lock and the first write operation
creates a RESERVED lock. Because the acquisition of locks is deferred until they
are needed, it is possible that another thread or process could create a separate
transaction and write to the database after the BEGIN on the current thread has
executed. If the transaction is immediate, then RESERVED locks are acquired on all
databases as soon as the BEGIN command is executed, without waiting for the database
to be used. After a BEGIN IMMEDIATE, you are guaranteed that no other thread or
process will be able to write to the database or do a BEGIN IMMEDIATE or BEGIN EXCLUSIVE.
Other processes can continue to read from the database, however. An exclusive transaction
causes EXCLUSIVE locks to be acquired on all databases. After a BEGIN EXCLUSIVE,
you are guaranteed that no other thread or process will be able to read or write
the database until the transaction is complete.
</p>
<p>
A description of the meaning of SHARED, RESERVED, and EXCLUSIVE locks is available
<a href="lockingv3.html">separately</a>.
</p>
<p>
The default behavior for SQLite version 3.0.8 is a deferred transaction. For SQLite
version 3.0.0 through 3.0.7, deferred is the only kind of transaction available.
For SQLite version 2.8 and earlier, all transactions are exclusive.
</p>
<p>
The COMMIT command does not actually perform a commit until all pending SQL commands
finish. Thus if two or more SELECT statements are in the middle of processing and
a COMMIT is executed, the commit will not actually occur until all SELECT statements
finish.
</p>
<p>
An attempt to execute COMMIT might result in an SQLITE_BUSY return code. This indicates
that another thread or process had a read lock on the database that prevented the
database from being updated. When COMMIT fails in this way, the transaction remains
active and the COMMIT can be retried later after the reader has had a chance to
clear.
</p>
<p>
<hr>
</p>
<div id="footer">
<p>
</p>
<p>
</p>
</div>
</div>
</div>
</body>
</html>
?? 快捷鍵說明
復制代碼
Ctrl + C
搜索代碼
Ctrl + F
全屏模式
F11
切換主題
Ctrl + Shift + D
顯示快捷鍵
?
增大字號
Ctrl + =
減小字號
Ctrl + -