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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(
sqlite3*,
const char *zDb,
const char *zTable,
const char *zColumn,
sqlite3_int64 iRow,
int flags,
sqlite3_blob **ppBlob
);
</pre></blockquote><p>
This interfaces opens a <a href="../c3ref/blob.html">handle</a> to the BLOB located
in row iRow, column zColumn, table zTable in database zDb;
in other words, the same BLOB that would be selected by:</p>
<p><pre>
SELECT zColumn FROM zDb.zTable WHERE <a href="../lang_createtable.html#rowid">rowid</a> = iRow;
</pre></p>
<p>If the flags parameter is non-zero, then the BLOB is opened for read
and write access. If it is zero, the BLOB is opened for read access.
It is not possible to open a column that is part of an index or primary
key for writing. If <a href="../foreignkeys.html">foreign key constraints</a> are enabled, it is
not possible to open a column that is part of a <a href="../foreignkeys.html#parentchild">child key</a> for writing.</p>
<p>Note that the database name is not the filename that contains
the database but rather the symbolic name of the database that
appears after the AS keyword when the database is connected using <a href="../lang_attach.html">ATTACH</a>.
For the main database file, the database name is "main".
For TEMP tables, the database name is "temp".</p>
<p>On success, <a href="../rescode.html#ok">SQLITE_OK</a> is returned and the new <a href="../c3ref/blob.html">BLOB handle</a> is written
to *ppBlob. Otherwise an <a href="../rescode.html">error code</a> is returned and *ppBlob is set
to be a null pointer.
This function sets the <a href="../c3ref/sqlite3.html">database connection</a> error code and message
accessible via <a href="../c3ref/errcode.html">sqlite3_errcode()</a> and <a href="../c3ref/errcode.html">sqlite3_errmsg()</a> and related
functions. Note that the *ppBlob variable is always initialized in a
way that makes it safe to invoke <a href="../c3ref/blob_close.html">sqlite3_blob_close()</a> on *ppBlob
regardless of the success or failure of this routine.</p>
<p>If the row that a BLOB handle points to is modified by an
<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
then the BLOB handle is marked as "expired".
This is true if any column of the row is changed, even a column
other than the one the BLOB handle is open on.
Calls to <a href="../c3ref/blob_read.html">sqlite3_blob_read()</a> and <a href="../c3ref/blob_write.html">sqlite3_blob_write()</a> for
an expired BLOB handle fail with a return code of <a href="../rescode.html#abort">SQLITE_ABORT</a>.
Changes written into a BLOB prior to the BLOB expiring are not
rolled back by the expiration of the BLOB. Such changes will eventually
commit if the transaction continues to completion.</p>
<p>Use the <a href="../c3ref/blob_bytes.html">sqlite3_blob_bytes()</a> interface to determine the size of
the opened blob. The size of a blob may not be changed by this
interface. Use the <a href="../lang_update.html">UPDATE</a> SQL command to change the size of a
blob.</p>
<p>The <a href="../c3ref/blob_open.html">sqlite3_blob_open()</a> interface will fail for a <a href="../withoutrowid.html">WITHOUT ROWID</a>
table. Incremental BLOB I/O is not possible on <a href="../withoutrowid.html">WITHOUT ROWID</a> tables.</p>
<p>The <a href="../c3ref/bind_blob.html">sqlite3_bind_zeroblob()</a> and <a href="../c3ref/result_blob.html">sqlite3_result_zeroblob()</a> interfaces
and the built-in <a href="../lang_corefunc.html#zeroblob">zeroblob</a> SQL function can be used, if desired,
to create an empty, zero-filled blob in which to read or write using
this interface.</p>
<p>To avoid a resource leak, every open <a href="../c3ref/blob.html">BLOB handle</a> should eventually
be released by a call to <a href="../c3ref/blob_close.html">sqlite3_blob_close()</a>.
</p><p>See also lists of
<a href="objlist.html">Objects</a>,
<a href="constlist.html">Constants</a>, and
<a href="funclist.html">Functions</a>.</p>
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