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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 routinereturns meta-data about a specific column of a specific databasetable accessible using the connection handle passed as the first functionargument.</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 as the database engine uses 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>Meta information is returned by writing to the memory locations passed asthe 5th and subsequent parameters to this function. Any of thesearguments may be NULL, in which case the corresponding element of metainformation is ommitted.</p><p><pre>Parameter Output Type Description-----------------------------------</p><p>5th const char* Data type6th const char* Name of the default collation sequence7th int True if the column has a NOT NULL constraint8th int True if the column is part of the PRIMARY KEY9th int True if the column is AUTOINCREMENT</pre></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, then an error is returned.</p><p>If the specified column is "rowid", "oid" or "_rowid_" and anINTEGER PRIMARY KEY column has been explicitly declared, then the outputparameters are set for the explicitly declared column. If there is noexplicitly declared IPK column, then the output parameters are set asfollows:</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 SQLITE error code is returned and an error messageleft in the database handle (to be retrieved using sqlite3_errmsg()).</p><p>This API is only available if the library was compiled with theSQLITE_ENABLE_COLUMN_METADATA 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 2008/01/31 20:37:13 UTC</i></small></div></body></html>⌨️ 快捷键说明
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