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+<div class=fancy>
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+<div class="fancy_title">
+Transaction
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+</div>
+
+
+
+
+<h1 id="transaction_control_syntax"><span>1. </span>Transaction Control Syntax</h1>
+
+<p><b><a href="syntax/begin-stmt.html">begin-stmt:</a></b>
+<button id='x2131' onclick='hideorshow("x2131","x2132")'>hide</button></p>
+ <div id='x2132' class='imgcontainer'>
+ <div style="max-width:560px"><svg xmlns='http://www.w3.org/2000/svg' class="pikchr" viewBox="0 0 560.669 140.4">
+<circle cx="5" cy="17" r="3.6"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
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+<text x="66" y="17" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">BEGIN</text>
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+<text x="219" y="123" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">EXCLUSIVE</text>
+<polygon points="299,123 287,127 287,118" style="fill:rgb(0,0,0)"/>
+<path d="M276,123L293,123"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
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+<path d="M444,47 L 511,47 Q 526,47 526,32 L 526,32 Q 526,17 533,17 L 541,17"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
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+<text x="217" y="47" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">DEFERRED</text>
+<polygon points="295,47 284,51 284,43" style="fill:rgb(0,0,0)"/>
+<path d="M272,47L289,47"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<path d="M295,47 L 304,47 Q 314,47 314,40 L 314,32"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
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+<text x="221" y="85" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">IMMEDIATE</text>
+<polygon points="304,85 292,89 292,81" style="fill:rgb(0,0,0)"/>
+<path d="M281,85L298,85"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<path d="M304,85 L 309,85 Q 314,85 314,77 L 314,70"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+</svg>
+</div>
+</div>
+<p><b><a href="syntax/commit-stmt.html">commit-stmt:</a></b>
+<button id='x2133' onclick='hideorshow("x2133","x2134")'>hide</button></p>
+ <div id='x2134' class='imgcontainer'>
+ <div style="max-width:434px"><svg xmlns='http://www.w3.org/2000/svg' class="pikchr" viewBox="0 0 434.506 72.36">
+<circle cx="5" cy="17" r="3.6"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
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+<path d="M83,32L141,32A15 15 0 0 0 157 17A15 15 0 0 0 141 2L83,2A15 15 0 0 0 68 17A15 15 0 0 0 83 32Z"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<text x="112" y="17" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">COMMIT</text>
+<polygon points="202,17 190,21 190,12" style="fill:rgb(0,0,0)"/>
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+<path d="M202,17L238,17"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<path d="M253,32L365,32A15 15 0 0 0 380 17A15 15 0 0 0 365 2L253,2A15 15 0 0 0 238 17A15 15 0 0 0 253 32Z"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<text x="309" y="17" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">TRANSACTION</text>
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+<text x="94" y="55" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">END</text>
+<polygon points="68,55 56,59 56,50" style="fill:rgb(0,0,0)"/>
+<path d="M32,17 L 39,17 Q 47,17 47,32 L 47,40 Q 47,55 55,55 L 62,55"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<polygon points="157,55 145,59 145,50" style="fill:rgb(0,0,0)"/>
+<path d="M119,55L151,55"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<path d="M157,55 L 164,55 Q 172,55 172,40 L 172,32 Q 172,17 179,17 L 187,17"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
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+</svg>
+</div>
+</div>
+<p><b><a href="syntax/rollback-stmt.html">rollback-stmt:</a></b>
+<button id='x2135' onclick='hideorshow("x2135","x2136")'>hide</button></p>
+ <div id='x2136' class='imgcontainer'>
+ <div style="max-width:801px"><svg xmlns='http://www.w3.org/2000/svg' class="pikchr" viewBox="0 0 801.734 67.392">
+<circle cx="5" cy="33" r="3.6"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
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+<path d="M47,48L125,48A15 15 0 0 0 140 33A15 15 0 0 0 125 18L47,18A15 15 0 0 0 32 33A15 15 0 0 0 47 48Z"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<text x="86" y="33" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">ROLLBACK</text>
+<polygon points="176,33 164,38 164,29" style="fill:rgb(0,0,0)"/>
+<path d="M140,33L170,33"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<path d="M191,48L303,48A15 15 0 0 0 318 33A15 15 0 0 0 303 18L191,18A15 15 0 0 0 176 33A15 15 0 0 0 191 48Z"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<text x="247" y="33" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">TRANSACTION</text>
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+<path d="M318,33L384,33"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<path d="M405,48L411,48A15 15 0 0 0 426 33A15 15 0 0 0 411 18L405,18A15 15 0 0 0 390 33A15 15 0 0 0 405 48Z"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<text x="408" y="33" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">TO</text>
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+<path d="M477,48L561,48A15 15 0 0 0 576 33A15 15 0 0 0 561 18L477,18A15 15 0 0 0 462 33A15 15 0 0 0 477 48Z"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
+<text x="519" y="33" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">SAVEPOINT</text>
+<polygon points="612,33 601,38 601,29" style="fill:rgb(0,0,0)"/>
+<path d="M576,33L606,33"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
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+<text x="684" y="33" text-anchor="middle" fill="rgb(0,0,0)" dominant-baseline="central">savepoint-name</text>
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+<path d="M519,6 L 576,6 Q 591,6 591,20 Q 591,33 599,33 L 606,33"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
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+<path d="M519,60 L 756,60 Q 771,60 771,47 Q 771,33 778,33 L 786,33"  style="fill:none;stroke-width:2.16;stroke:rgb(0,0,0);" />
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+</div>
+</div>
+
+
+<h1 id="transactions"><span>2. </span>Transactions</h1>
+
+<p>
+No reads or writes occur except within a transaction.
+Any command that accesses the database (basically, any SQL command,
+except a few <a href="pragma.html#syntax">PRAGMA</a> statements)
+will automatically start a transaction if
+one is not already in effect.  Automatically started transactions
+are committed when the last SQL statement finishes.
+</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>
+END TRANSACTION is an alias for COMMIT.
+</p>
+
+<p> Transactions created using BEGIN...COMMIT do not nest.
+For nested transactions, use the <a href="lang_savepoint.html">SAVEPOINT</a> and <a href="lang_savepoint.html">RELEASE</a> commands.
+The "TO SAVEPOINT <span class='yyterm'>name</span>" clause of the ROLLBACK command shown
+in the syntax diagram above is only applicable to <a href="lang_savepoint.html">SAVEPOINT</a>
+transactions.  An attempt to invoke the BEGIN command within
+a transaction will fail with an error, regardless of whether
+the transaction was started by <a href="lang_savepoint.html">SAVEPOINT</a> or a prior BEGIN.
+The COMMIT command and the ROLLBACK command without the TO clause
+work the same on <a href="lang_savepoint.html">SAVEPOINT</a> transactions as they do with transactions
+started by BEGIN.</p>
+
+<h2 id="read_transactions_versus_write_transactions"><span>2.1. </span>Read transactions versus write transactions</h2>
+
+<p>SQLite supports multiple simultaneous read transactions
+coming from separate database connections, possibly in separate
+threads or processes, but only one simultaneous write transaction.
+</p><p>
+
+</p><p>A read transaction is used for reading only.  A write transaction
+allows both reading and writing.  A read transaction is started
+by a SELECT statement, and a write transaction is started by 
+statements like CREATE, DELETE, DROP, INSERT, or UPDATE (collectively
+"write statements").  If a write statement occurs while
+a read transaction is active, then the read transaction is upgraded
+to a write transaction if possible.  If some other database connection
+has already modified the database or is already in the process of
+modifying the database, then upgrading to a write transaction is
+not possible and the write statement will fail with <a href="rescode.html#busy">SQLITE_BUSY</a>.
+</p>
+
+<p>
+While a read transaction is active, any changes to the database that
+are implemented by separate database connections will not be seen
+by the database connection that started the read transaction.  If database
+connection X is holding a read transaction, it is possible that some
+other database connection Y might change the content of the database
+while X's transaction is still open, however X will not be able to see 
+those changes until after the transaction ends.  While its read
+transaction is active, X will continue to see an historic snapshot of
+the database prior to the changes implemented by Y.
+</p>
+
+
+<a name="immediate"></a>
+
+<h2 id="deferred_immediate_and_exclusive_transactions"><span>2.2. </span>DEFERRED, IMMEDIATE, and EXCLUSIVE transactions</h2>
+
+<p>
+Transactions can be DEFERRED, IMMEDIATE, or EXCLUSIVE.
+The default transaction behavior is DEFERRED.
+</p>
+
+<p>
+DEFERRED means that the transaction does not actually
+start until the database is first accessed.  Internally,
+the BEGIN DEFERRED statement merely sets a flag on the database 
+connection that turns off the automatic commit that would normally
+occur when the last statement finishes.  This causes the transaction
+that is automatically started to persist until an explicit
+COMMIT or ROLLBACK or until a rollback is provoked by an error
+or an ON CONFLICT ROLLBACK clause.  If the first statement after
+BEGIN DEFERRED is a SELECT, then a read transaction is started.
+Subsequent write statements will upgrade the transaction to a
+write transaction if possible, or return SQLITE_BUSY.  If the
+first statement after BEGIN DEFERRED is a write statement, then
+a write transaction is started.
+</p>
+
+<p>
+IMMEDIATE cause the database connection to start a new write
+immediately, without waiting for a write statement.  The 
+BEGIN IMMEDIATE might fail with <a href="rescode.html#busy">SQLITE_BUSY</a> if another write
+transaction is already active on another database connection.
+</p>
+
+<p>
+EXCLUSIVE is similar to IMMEDIATE in that a write transaction
+is started immediately.  EXCLUSIVE and IMMEDIATE are the same
+in <a href="wal.html">WAL mode</a>, but in other journaling modes, EXCLUSIVE prevents
+other database connections from reading the database while the
+transaction is underway.
+</p>
+
+<h2 id="implicit_versus_explicit_transactions"><span>2.3. </span>Implicit versus explicit transactions</h2>
+
+<p>
+An implicit transaction (a transaction that is started automatically,
+not a transaction started by BEGIN) is committed automatically when
+the last active statement finishes.  A statement finishes when its
+last cursor closes, which is guaranteed to happen when the
+prepared statement is <a href="c3ref/reset.html">reset</a> or
+<a href="c3ref/finalize.html">finalized</a>.  Some statements might "finish"
+for the purpose of transaction control prior to being reset or finalized,
+but there is no guarantee of this.  The only way to ensure that a
+statement has "finished" is to invoke <a href="c3ref/reset.html">sqlite3_reset()</a> or
+<a href="c3ref/finalize.html">sqlite3_finalize()</a> on that statement.  An open <a href="c3ref/blob.html">sqlite3_blob</a> used for
+incremental BLOB I/O also counts as an unfinished statement.
+The <a href="c3ref/blob.html">sqlite3_blob</a> finishes when it is <a href="c3ref/blob_close.html">closed</a>.
+</p>
+
+<p>
+The explicit COMMIT command runs immediately, even if there are
+pending <a href="lang_select.html">SELECT</a> statements.  However, if there are pending
+write operations, the COMMIT command
+will fail with an error code <a href="rescode.html#busy">SQLITE_BUSY</a>.
+</p>
+
+<p>
+An attempt to execute COMMIT might also result in an <a href="rescode.html#busy">SQLITE_BUSY</a> return code
+if an another thread or process has an open read connection.
+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>
+In very old versions of SQLite (before version 3.7.11 - 2012-03-20)
+the ROLLBACK will fail with an error code 
+<a href="rescode.html#busy">SQLITE_BUSY</a> if there are any pending queries.  In more recent
+versions of SQLite, the ROLLBACK will proceed and pending statements
+will often be aborted, causing them to return an <a href="rescode.html#abort">SQLITE_ABORT</a> or
+<a href="rescode.html#abort_rollback">SQLITE_ABORT_ROLLBACK</a> error.
+In SQLite version 3.8.8 (2015-01-16) and later,
+a pending read will continue functioning
+after the ROLLBACK as long as the ROLLBACK does not modify the database
+schema.
+</p>
+
+<p>
+If <a href="pragma.html#pragma_journal_mode">PRAGMA journal_mode</a> is set to OFF (thus disabling the rollback journal
+file) then the behavior of the ROLLBACK command is undefined.
+</p>
+
+<h1 id="response_to_errors_within_a_transaction"><span>3. </span>Response To Errors Within A Transaction</h1>
+
+<p> If certain kinds of errors occur within a transaction, the
+transaction may or may not be rolled back automatically.  The
+errors that can cause an automatic rollback include:</p>
+
+<ul>
+<li> <a href="rescode.html#full">SQLITE_FULL</a>: database or disk full
+</li><li> <a href="rescode.html#ioerr">SQLITE_IOERR</a>: disk I/O error
+</li><li> <a href="rescode.html#busy">SQLITE_BUSY</a>: database in use by another process
+</li><li> <a href="rescode.html#nomem">SQLITE_NOMEM</a>: out of memory
+</li></ul>
+
+<p>
+For all of these errors, SQLite attempts to undo just the one statement
+it was working on and leave changes from prior statements within the
+same transaction intact and continue with the transaction.  However, 
+depending on the statement being evaluated and the point at which the
+error occurs, it might be necessary for SQLite to rollback and
+cancel the entire transaction.  An application can tell which
+course of action SQLite took by using the
+<a href="c3ref/get_autocommit.html">sqlite3_get_autocommit()</a> C-language interface.</p>
+
+<p>It is recommended that applications respond to the errors
+listed above by explicitly issuing a ROLLBACK command.  If the 
+transaction has already been rolled back automatically
+by the error response, then the ROLLBACK command will fail with an
+error, but no harm is caused by this.</p>
+
+<p>Future versions of SQLite may extend the list of errors which
+might cause automatic transaction rollback.  Future versions of
+SQLite might change the error response.  In particular, we may
+choose to simplify the interface in future versions of SQLite by
+causing the errors above to force an unconditional rollback.</p>
+<p align="center"><small><i>This page last modified on  <a href="https://sqlite.org/docsrc/honeypot" id="mtimelink"  data-href="https://sqlite.org/docsrc/finfo/pages/lang_transaction.in?m=44e02f89eb1112b5a">2020-07-09 15:12:58</a> UTC </small></i></p>
+