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<a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Open A BLOB For Incremental I/O</h2><blockquote><pre>int sqlite3_blob_open(
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sqlite3_blob **ppBlob
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</pre></blockquote><p>
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This interfaces opens a <a href="../c3ref/blob.html">handle</a> to the BLOB located
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in row iRow, column zColumn, table zTable in database zDb;
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in other words, the same BLOB that would be selected by:</p>
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SELECT zColumn FROM zDb.zTable WHERE <a href="../lang_createtable.html#rowid">rowid</a> = iRow;
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<p>If the flags parameter is non-zero, then the BLOB is opened for read
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and write access. If it is zero, the BLOB is opened for read access.
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It is not possible to open a column that is part of an index or primary
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key for writing. If <a href="../foreignkeys.html">foreign key constraints</a> are enabled, it is
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not possible to open a column that is part of a <a href="../foreignkeys.html#parentchild">child key</a> for writing.</p>
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<p>Note that the database name is not the filename that contains
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the database but rather the symbolic name of the database that
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appears after the AS keyword when the database is connected using <a href="../lang_attach.html">ATTACH</a>.
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For the main database file, the database name is "main".
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For TEMP tables, the database name is "temp".</p>
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<p>On success, <a href="../c3ref/c_abort.html">SQLITE_OK</a> is returned and the new <a href="../c3ref/blob.html">BLOB handle</a> is written
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to *ppBlob. Otherwise an <a href="../c3ref/c_abort.html">error code</a> is returned and *ppBlob is set
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to be a null pointer.
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This function sets the <a href="../c3ref/sqlite3.html">database connection</a> error code and message
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accessible via <a href="../c3ref/errcode.html">sqlite3_errcode()</a> and <a href="../c3ref/errcode.html">sqlite3_errmsg()</a> and related
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functions. Note that the *ppBlob variable is always initialized in a
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way that makes it safe to invoke <a href="../c3ref/blob_close.html">sqlite3_blob_close()</a> on *ppBlob
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regardless of the success or failure of this routine.</p>
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<p>If the row that a BLOB handle points to is modified by an
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<a href="../lang_update.html">UPDATE</a>, <a href="../lang_delete.html">DELETE</a>, or by <a href="../lang_conflict.html">ON CONFLICT</a> side-effects
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then the BLOB handle is marked as "expired".
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This is true if any column of the row is changed, even a column
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other than the one the BLOB handle is open on.
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Calls to <a href="../c3ref/blob_read.html">sqlite3_blob_read()</a> and <a href="../c3ref/blob_write.html">sqlite3_blob_write()</a> for
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an expired BLOB handle fail with a return code of <a href="../c3ref/c_abort.html">SQLITE_ABORT</a>.
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Changes written into a BLOB prior to the BLOB expiring are not
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rolled back by the expiration of the BLOB. Such changes will eventually
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commit if the transaction continues to completion.</p>
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<p>Use the <a href="../c3ref/blob_bytes.html">sqlite3_blob_bytes()</a> interface to determine the size of
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the opened blob. The size of a blob may not be changed by this
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interface. Use the <a href="../lang_update.html">UPDATE</a> SQL command to change the size of a
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<p>The <a href="../c3ref/bind_blob.html">sqlite3_bind_zeroblob()</a> and <a href="../c3ref/result_blob.html">sqlite3_result_zeroblob()</a> interfaces
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and the built-in <a href="../lang_corefunc.html#zeroblob">zeroblob</a> SQL function can be used, if desired,
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to create an empty, zero-filled blob in which to read or write using
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<p>To avoid a resource leak, every open <a href="../c3ref/blob.html">BLOB handle</a> should eventually
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be released by a call to <a href="../c3ref/blob_close.html">sqlite3_blob_close()</a>.
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</p><p>See also lists of
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<a href="objlist.html">Objects</a>,
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<a href="constlist.html">Constants</a>, and
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<a href="funclist.html">Functions</a>.</p>
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