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<h1 align="center">SQL As Understood By SQLite</h1><p><a href="lang.html">[Top]</a></p><h2>ATTACH DATABASE</h2><h4><a href="syntaxdiagrams.html#attach-stmt">attach-stmt:</a></h4><blockquote> <img alt="syntax diagram attach-stmt" src="images/syntax/attach-stmt.gif"></img> </blockquote>
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<p> The ATTACH DATABASE statement adds another database
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file to the current <a href="c3ref/sqlite3.html">database connection</a>.
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The filename for the database to be attached is the value of
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the expression that occurs before the AS keyword.
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The filename of the database follows the same semantics as the
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filename argument to <a href="c3ref/open.html">sqlite3_open()</a> and <a href="c3ref/open.html">sqlite3_open_v2()</a>; the
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special name "<a href="inmemorydb.html">:memory:</a>" results in an <a href="inmemorydb.html">in-memory database</a> and an
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empty string results in a new temporary database.
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The filename argument can be a <a href="uri.html">URI filename</a> if URI filename processing
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is enable on the database connection. The default behavior is for
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URI filenames to be disabled, however that might change in a future release
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of SQLite, so application developers are advised to plan accordingly.
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<p>The name that occurs after the AS keyword is the name of the database
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used internally by SQLite.
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The database-names 'main' and
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'temp' refer to the main database and the database used for
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temporary tables. The main and temp databases cannot be attached or
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<p> Tables in an attached database can be referred to using the syntax
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<i>database-name.table-name</i>. If the name of the table is unique
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across all attached databases and the main and temp databases, then the
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<i>database-name</i> prefix is not required. If two or more tables in
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different databases have the same name and the
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<i>database-name</i> prefix is not used on a table reference, then the
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table chosen is the one in the database that was least recently attached.</p>
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Transactions involving multiple attached databases are atomic,
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assuming that the main database is not "<a href="inmemorydb.html">:memory:</a>" and the
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<a href="pragma.html#pragma_journal_mode">journal_mode</a> is not <a href="wal.html">WAL</a>. If the main
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database is ":memory:" or if the journal_mode is WAL, then
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transactions continue to be atomic within each individual
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database file. But if the host computer crashes in the middle
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of a <a href="lang_transaction.html">COMMIT</a> where two or more database files are updated,
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some of those files might get the changes where others
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<p> There is a limit, set using <a href="c3ref/limit.html">sqlite3_limit()</a> and
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<a href="c3ref/c_limit_attached.html#sqlitelimitattached">SQLITE_LIMIT_ATTACHED</a>, to the number of databases that can be
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simultaneously attached to a single database connection.</p>
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