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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"><html><head><title>Extract Metadata About A Column Of A Table</title><style type="text/css">body { margin: auto; font-family: "Verdana" "sans-serif"; padding: 8px 1%;}a { color: #45735f }a:visited { color: #734559 }.logo { position:absolute; margin:3px; }.tagline { float:right; text-align:right; font-style:italic; width:240px; margin:12px; margin-top:58px;}.toolbar { font-variant: small-caps; text-align: center; line-height: 1.6em; margin: 0; padding:1px 8px;}.toolbar a { color: white; text-decoration: none; padding: 6px 12px; }.toolbar a:visited { color: white; }.toolbar a:hover { color: #80a796; background: white; }.content { margin: 5%; }.content dt { font-weight:bold; }.content dd { margin-bottom: 25px; margin-left:20%; }.content ul { padding:0px; padding-left: 15px; margin:0px; }/* rounded corners */.se { background: url(../images/se.png) 100% 100% no-repeat #80a796}.sw { background: url(../images/sw.png) 0% 100% no-repeat }.ne { background: url(../images/ne.png) 100% 0% no-repeat }.nw { background: url(../images/nw.png) 0% 0% no-repeat }</style><meta http-equiv="content-type" content="text/html; charset=UTF-8"> </head><body><div><!-- container div to satisfy validator --><a href="../index.html"><img class="logo" src="../images/SQLite.gif" alt="SQLite Logo" border="0"></a><div><!-- IE hack to prevent disappearing logo--></div><div class="tagline">Small. 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Reliable.<br>Choose any three.</div><table width=100% style="clear:both"><tr><td> <div class="se"><div class="sw"><div class="ne"><div class="nw"> <div class="toolbar"> <a href="../about.html">About</a> <a href="../sitemap.html">Sitemap</a> <a href="../docs.html">Documentation</a> <a href="../download.html">Download</a> <a href="../copyright.html">License</a> <a href="../news.html">News</a> <a href="http://www.sqlite.org/cvstrac/index">Developers</a> <a href="../support.html">Support</a> </div></div></div></div></div></td></tr></table> <a href="intro.html"><h2>SQLite C Interface</h2></a><h2>Extract Metadata About A Column Of A Table</h2><blockquote><pre>int sqlite3_table_column_metadata( sqlite3 *db, /* Connection handle */ const char *zDbName, /* Database name or NULL */ const char *zTableName, /* Table name */ const char *zColumnName, /* Column name */ char const **pzDataType, /* OUTPUT: Declared data type */ char const **pzCollSeq, /* OUTPUT: Collation sequence name */ int *pNotNull, /* OUTPUT: True if NOT NULL constraint exists */ int *pPrimaryKey, /* OUTPUT: True if column part of PK */ int *pAutoinc /* OUTPUT: True if column is auto-increment */);</pre></blockquote><p>This routine returns metadata about a specific column of a specificdatabase table accessible using the <a href="../c3ref/sqlite3.html">database connection</a> handlepassed as the first function argument.</p><p>The column is identified by the second, third and fourth parameters tothis function. The second parameter is either the name of the database(i.e. "main", "temp" or an attached database) containing the specifiedtable or NULL. If it is NULL, then all attached databases are searchedfor the table using the same algorithm used by the database engine toresolve unqualified table references.</p><p>The third and fourth parameters to this function are the table and columnname of the desired column, respectively. Neither of these parametersmay be NULL.</p><p>Metadata is returned by writing to the memory locations passed as the 5thand subsequent parameters to this function. Any of these arguments may beNULL, in which case the corresponding element of metadata is omitted.</p><p><blockquote><table border="1"><tr><th> Parameter <th> Output<br>Type <th> Description</p><p><tr><td> 5th <td> const char* <td> Data type<tr><td> 6th <td> const char* <td> Name of default collation sequence<tr><td> 7th <td> int <td> True if column has a NOT NULL constraint<tr><td> 8th <td> int <td> True if column is part of the PRIMARY KEY<tr><td> 9th <td> int <td> True if column is <a href="../autoinc.html">AUTOINCREMENT</a></table></blockquote></p><p>The memory pointed to by the character pointers returned for thedeclaration type and collation sequence is valid only until the nextcall to any SQLite API function.</p><p>If the specified table is actually a view, an <a href="../c3ref/c_abort.html">error code</a> is returned.</p><p>If the specified column is "rowid", "oid" or "_rowid_" and an<a href="../lang_createtable.html#rowid">INTEGER PRIMARY KEY</a> column has been explicitly declared, then the outputparameters are set for the explicitly declared column. If there is noexplicitly declared <a href="../lang_createtable.html#rowid">INTEGER PRIMARY KEY</a> column, then the outputparameters are set as follows:</p><p><pre>data type: "INTEGER"collation sequence: "BINARY"not null: 0primary key: 1auto increment: 0</pre></p><p>This function may load one or more schemas from database files. If anerror occurs during this process, or if the requested table or columncannot be found, an <a href="../c3ref/c_abort.html">error code</a> is returned and an error message leftin the <a href="../c3ref/sqlite3.html">database connection</a> (to be retrieved using sqlite3_errmsg()).</p><p>This API is only available if the library was compiled with the<a href="../compile.html#enable_column_metadata">SQLITE_ENABLE_COLUMN_METADATA</a> C-preprocessor symbol defined.</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><hr><small><i>This page last modified 2008/12/09 18:44:04 UTC</i></small></div></body></html>⌨️ 快捷键说明
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