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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-13 14:07:11 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-13 14:07:11 +0000
commit63847496f14c813a5d80efd5b7de0f1294ffe1e3 (patch)
tree01c7571c7c762ceee70638549a99834fdd7c411b /www/c3ref/column_blob.html
parentInitial commit. (diff)
downloadsqlite3-63847496f14c813a5d80efd5b7de0f1294ffe1e3.tar.xz
sqlite3-63847496f14c813a5d80efd5b7de0f1294ffe1e3.zip
Adding upstream version 3.45.1.upstream/3.45.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+<!DOCTYPE html>
+<html><head>
+<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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+<title>Result Values From A Query</title>
+<!-- path=../ -->
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+<body>
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+if( !location.origin || !location.origin.match || !location.origin.match(/http/) ){
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+/* Used by the Hide/Show button beside syntax diagrams, to toggle the */
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+<!-- keywords: {column access functions} sqlite3_column_blob sqlite3_column_bytes sqlite3_column_bytes16 sqlite3_column_double sqlite3_column_int sqlite3_column_int64 sqlite3_column_text sqlite3_column_text16 sqlite3_column_type sqlite3_column_value -->
+<div class=nosearch>
+<a href="../c3ref/intro.html"><h2>SQLite C Interface</h2></a>
+<h2>Result Values From A Query</h2>
+</div>
+<blockquote><pre>
+const void *sqlite3_column_blob(sqlite3_stmt*, int iCol);
+double sqlite3_column_double(sqlite3_stmt*, int iCol);
+int sqlite3_column_int(sqlite3_stmt*, int iCol);
+sqlite3_int64 sqlite3_column_int64(sqlite3_stmt*, int iCol);
+const unsigned char *sqlite3_column_text(sqlite3_stmt*, int iCol);
+const void *sqlite3_column_text16(sqlite3_stmt*, int iCol);
+sqlite3_value *sqlite3_column_value(sqlite3_stmt*, int iCol);
+int sqlite3_column_bytes(sqlite3_stmt*, int iCol);
+int sqlite3_column_bytes16(sqlite3_stmt*, int iCol);
+int sqlite3_column_type(sqlite3_stmt*, int iCol);
+</pre></blockquote>
+<p>
+<b>Summary:</b>
+<blockquote><table border=0 cellpadding=0 cellspacing=0>
+<tr><td><b>sqlite3_column_blob</b><td>&rarr;<td>BLOB result
+<tr><td><b>sqlite3_column_double</b><td>&rarr;<td>REAL result
+<tr><td><b>sqlite3_column_int</b><td>&rarr;<td>32-bit INTEGER result
+<tr><td><b>sqlite3_column_int64</b><td>&rarr;<td>64-bit INTEGER result
+<tr><td><b>sqlite3_column_text</b><td>&rarr;<td>UTF-8 TEXT result
+<tr><td><b>sqlite3_column_text16</b><td>&rarr;<td>UTF-16 TEXT result
+<tr><td><b>sqlite3_column_value</b><td>&rarr;<td>The result as an
+<a href="../c3ref/value.html">unprotected sqlite3_value</a> object.
+<tr><td>&nbsp;<td>&nbsp;<td>&nbsp;
+<tr><td><b>sqlite3_column_bytes</b><td>&rarr;<td>Size of a BLOB
+or a UTF-8 TEXT result in bytes
+<tr><td><b>sqlite3_column_bytes16&nbsp;&nbsp;</b>
+<td>&rarr;&nbsp;&nbsp;<td>Size of UTF-16
+TEXT in bytes
+<tr><td><b>sqlite3_column_type</b><td>&rarr;<td>Default
+datatype of the result
+</table></blockquote></p>
+
+<p><b>Details:</b></p>
+
+<p>These routines return information about a single column of the current
+result row of a query. In every case the first argument is a pointer
+to the <a href="../c3ref/stmt.html">prepared statement</a> that is being evaluated (the <a href="../c3ref/stmt.html">sqlite3_stmt*</a>
+that was returned from <a href="../c3ref/prepare.html">sqlite3_prepare_v2()</a> or one of its variants)
+and the second argument is the index of the column for which information
+should be returned. The leftmost column of the result set has the index 0.
+The number of columns in the result can be determined using
+<a href="../c3ref/column_count.html">sqlite3_column_count()</a>.</p>
+
+<p>If the SQL statement does not currently point to a valid row, or if the
+column index is out of range, the result is undefined.
+These routines may only be called when the most recent call to
+<a href="../c3ref/step.html">sqlite3_step()</a> has returned <a href="../rescode.html#row">SQLITE_ROW</a> and neither
+<a href="../c3ref/reset.html">sqlite3_reset()</a> nor <a href="../c3ref/finalize.html">sqlite3_finalize()</a> have been called subsequently.
+If any of these routines are called after <a href="../c3ref/reset.html">sqlite3_reset()</a> or
+<a href="../c3ref/finalize.html">sqlite3_finalize()</a> or after <a href="../c3ref/step.html">sqlite3_step()</a> has returned
+something other than <a href="../rescode.html#row">SQLITE_ROW</a>, the results are undefined.
+If <a href="../c3ref/step.html">sqlite3_step()</a> or <a href="../c3ref/reset.html">sqlite3_reset()</a> or <a href="../c3ref/finalize.html">sqlite3_finalize()</a>
+are called from a different thread while any of these routines
+are pending, then the results are undefined.</p>
+
+<p>The first six interfaces (_blob, _double, _int, _int64, _text, and _text16)
+each return the value of a result column in a specific data format. If
+the result column is not initially in the requested format (for example,
+if the query returns an integer but the sqlite3_column_text() interface
+is used to extract the value) then an automatic type conversion is performed.</p>
+
+<p>The sqlite3_column_type() routine returns the
+<a href="../c3ref/c_blob.html">datatype code</a> for the initial data type
+of the result column. The returned value is one of <a href="../c3ref/c_blob.html">SQLITE_INTEGER</a>,
+<a href="../c3ref/c_blob.html">SQLITE_FLOAT</a>, <a href="../c3ref/c_blob.html">SQLITE_TEXT</a>, <a href="../c3ref/c_blob.html">SQLITE_BLOB</a>, or <a href="../c3ref/c_blob.html">SQLITE_NULL</a>.
+The return value of sqlite3_column_type() can be used to decide which
+of the first six interface should be used to extract the column value.
+The value returned by sqlite3_column_type() is only meaningful if no
+automatic type conversions have occurred for the value in question.
+After a type conversion, the result of calling sqlite3_column_type()
+is undefined, though harmless. Future
+versions of SQLite may change the behavior of sqlite3_column_type()
+following a type conversion.</p>
+
+<p>If the result is a BLOB or a TEXT string, then the sqlite3_column_bytes()
+or sqlite3_column_bytes16() interfaces can be used to determine the size
+of that BLOB or string.</p>
+
+<p>If the result is a BLOB or UTF-8 string then the sqlite3_column_bytes()
+routine returns the number of bytes in that BLOB or string.
+If the result is a UTF-16 string, then sqlite3_column_bytes() converts
+the string to UTF-8 and then returns the number of bytes.
+If the result is a numeric value then sqlite3_column_bytes() uses
+<a href="../c3ref/mprintf.html">sqlite3_snprintf()</a> to convert that value to a UTF-8 string and returns
+the number of bytes in that string.
+If the result is NULL, then sqlite3_column_bytes() returns zero.</p>
+
+<p>If the result is a BLOB or UTF-16 string then the sqlite3_column_bytes16()
+routine returns the number of bytes in that BLOB or string.
+If the result is a UTF-8 string, then sqlite3_column_bytes16() converts
+the string to UTF-16 and then returns the number of bytes.
+If the result is a numeric value then sqlite3_column_bytes16() uses
+<a href="../c3ref/mprintf.html">sqlite3_snprintf()</a> to convert that value to a UTF-16 string and returns
+the number of bytes in that string.
+If the result is NULL, then sqlite3_column_bytes16() returns zero.</p>
+
+<p>The values returned by <a href="../c3ref/column_blob.html">sqlite3_column_bytes()</a> and
+<a href="../c3ref/column_blob.html">sqlite3_column_bytes16()</a> do not include the zero terminators at the end
+of the string. For clarity: the values returned by
+<a href="../c3ref/column_blob.html">sqlite3_column_bytes()</a> and <a href="../c3ref/column_blob.html">sqlite3_column_bytes16()</a> are the number of
+bytes in the string, not the number of characters.</p>
+
+<p>Strings returned by sqlite3_column_text() and sqlite3_column_text16(),
+even empty strings, are always zero-terminated. The return
+value from sqlite3_column_blob() for a zero-length BLOB is a NULL pointer.</p>
+
+<p>Strings returned by sqlite3_column_text16() always have the endianness
+which is native to the platform, regardless of the text encoding set
+for the database.</p>
+
+<p><b>Warning:</b> The object returned by <a href="../c3ref/column_blob.html">sqlite3_column_value()</a> is an
+<a href="../c3ref/value.html">unprotected sqlite3_value</a> object. In a multithreaded environment,
+an unprotected sqlite3_value object may only be used safely with
+<a href="../c3ref/bind_blob.html">sqlite3_bind_value()</a> and <a href="../c3ref/result_blob.html">sqlite3_result_value()</a>.
+If the <a href="../c3ref/value.html">unprotected sqlite3_value</a> object returned by
+<a href="../c3ref/column_blob.html">sqlite3_column_value()</a> is used in any other way, including calls
+to routines like <a href="../c3ref/value_blob.html">sqlite3_value_int()</a>, <a href="../c3ref/value_blob.html">sqlite3_value_text()</a>,
+or <a href="../c3ref/value_blob.html">sqlite3_value_bytes()</a>, the behavior is not threadsafe.
+Hence, the sqlite3_column_value() interface
+is normally only useful within the implementation of
+<a href="../appfunc.html">application-defined SQL functions</a> or <a href="../vtab.html">virtual tables</a>, not within
+top-level application code.</p>
+
+<p>These routines may attempt to convert the datatype of the result.
+For example, if the internal representation is FLOAT and a text result
+is requested, <a href="../c3ref/mprintf.html">sqlite3_snprintf()</a> is used internally to perform the
+conversion automatically. The following table details the conversions
+that are applied:</p>
+
+<p><blockquote>
+<table border="1">
+<tr><th> Internal<br>Type <th> Requested<br>Type <th> Conversion</p>
+
+<p><tr><td> NULL <td> INTEGER <td> Result is 0
+<tr><td> NULL <td> FLOAT <td> Result is 0.0
+<tr><td> NULL <td> TEXT <td> Result is a NULL pointer
+<tr><td> NULL <td> BLOB <td> Result is a NULL pointer
+<tr><td> INTEGER <td> FLOAT <td> Convert from integer to float
+<tr><td> INTEGER <td> TEXT <td> ASCII rendering of the integer
+<tr><td> INTEGER <td> BLOB <td> Same as INTEGER->TEXT
+<tr><td> FLOAT <td> INTEGER <td> <a href="../lang_expr.html#castexpr">CAST</a> to INTEGER
+<tr><td> FLOAT <td> TEXT <td> ASCII rendering of the float
+<tr><td> FLOAT <td> BLOB <td> <a href="../lang_expr.html#castexpr">CAST</a> to BLOB
+<tr><td> TEXT <td> INTEGER <td> <a href="../lang_expr.html#castexpr">CAST</a> to INTEGER
+<tr><td> TEXT <td> FLOAT <td> <a href="../lang_expr.html#castexpr">CAST</a> to REAL
+<tr><td> TEXT <td> BLOB <td> No change
+<tr><td> BLOB <td> INTEGER <td> <a href="../lang_expr.html#castexpr">CAST</a> to INTEGER
+<tr><td> BLOB <td> FLOAT <td> <a href="../lang_expr.html#castexpr">CAST</a> to REAL
+<tr><td> BLOB <td> TEXT <td> <a href="../lang_expr.html#castexpr">CAST</a> to TEXT, ensure zero terminator
+</table>
+</blockquote></p>
+
+<p>Note that when type conversions occur, pointers returned by prior
+calls to sqlite3_column_blob(), sqlite3_column_text(), and/or
+sqlite3_column_text16() may be invalidated.
+Type conversions and pointer invalidations might occur
+in the following cases:</p>
+
+<p><ul>
+<li> The initial content is a BLOB and sqlite3_column_text() or
+sqlite3_column_text16() is called. A zero-terminator might
+need to be added to the string.</li>
+<li> The initial content is UTF-8 text and sqlite3_column_bytes16() or
+sqlite3_column_text16() is called. The content must be converted
+to UTF-16.</li>
+<li> The initial content is UTF-16 text and sqlite3_column_bytes() or
+sqlite3_column_text() is called. The content must be converted
+to UTF-8.</li>
+</ul></p>
+
+<p>Conversions between UTF-16be and UTF-16le are always done in place and do
+not invalidate a prior pointer, though of course the content of the buffer
+that the prior pointer references will have been modified. Other kinds
+of conversion are done in place when it is possible, but sometimes they
+are not possible and in those cases prior pointers are invalidated.</p>
+
+<p>The safest policy is to invoke these routines
+in one of the following ways:</p>
+
+<p><ul>
+<li>sqlite3_column_text() followed by sqlite3_column_bytes()</li>
+<li>sqlite3_column_blob() followed by sqlite3_column_bytes()</li>
+<li>sqlite3_column_text16() followed by sqlite3_column_bytes16()</li>
+</ul></p>
+
+<p>In other words, you should call sqlite3_column_text(),
+sqlite3_column_blob(), or sqlite3_column_text16() first to force the result
+into the desired format, then invoke sqlite3_column_bytes() or
+sqlite3_column_bytes16() to find the size of the result. Do not mix calls
+to sqlite3_column_text() or sqlite3_column_blob() with calls to
+sqlite3_column_bytes16(), and do not mix calls to sqlite3_column_text16()
+with calls to sqlite3_column_bytes().</p>
+
+<p>The pointers returned are valid until a type conversion occurs as
+described above, or until <a href="../c3ref/step.html">sqlite3_step()</a> or <a href="../c3ref/reset.html">sqlite3_reset()</a> or
+<a href="../c3ref/finalize.html">sqlite3_finalize()</a> is called. The memory space used to hold strings
+and BLOBs is freed automatically. Do not pass the pointers returned
+from <a href="../c3ref/column_blob.html">sqlite3_column_blob()</a>, <a href="../c3ref/column_blob.html">sqlite3_column_text()</a>, etc. into
+<a href="../c3ref/free.html">sqlite3_free()</a>.</p>
+
+<p>As long as the input parameters are correct, these routines will only
+fail if an out-of-memory error occurs during a format conversion.
+Only the following subset of interfaces are subject to out-of-memory
+errors:</p>
+
+<p><ul>
+<li> sqlite3_column_blob()
+<li> sqlite3_column_text()
+<li> sqlite3_column_text16()
+<li> sqlite3_column_bytes()
+<li> sqlite3_column_bytes16()
+</ul></p>
+
+<p>If an out-of-memory error occurs, then the return value from these
+routines is the same as if the column had contained an SQL NULL value.
+Valid SQL NULL returns can be distinguished from out-of-memory errors
+by invoking the <a href="../c3ref/errcode.html">sqlite3_errcode()</a> immediately after the suspect
+return value is obtained and before any
+other SQLite interface is called on the same <a href="../c3ref/sqlite3.html">database connection</a>.
+</p><p>See also lists of
+ <a href="../c3ref/objlist.html">Objects</a>,
+ <a href="../c3ref/constlist.html">Constants</a>, and
+ <a href="../c3ref/funclist.html">Functions</a>.</p>
+