<html> <head> <title>SQLite RDBMS</title> </head> <body bgcolor="#ffffff"> <h1>SQLite RDBMS</h1> <p>OGR optionally supports spatial and non-spatial tables stored in SQLite 3.x database files. SQLite is a "light weight" single file based RDBMS engine with fairly complete SQL semantics and respectible performance.</p> <p>The driver looks for a geometry_columns table layed out as defined loosely according to OGC Simple Features standards, particularly as defined in <A href="http://trac.osgeo.org/fdo/wiki/FDORfc16">FDO RFC 16</a>. If found it is used to map tables to layers.</P> <p>If geometry_columns is not found, each table is treated as a layer. Layers with a WKT_GEOMETRY field will be treated as spatial tables, and the WKT_GEOMETRY column will be read as Well Known Text geometry.</p> <p>If geometry_columns is found, it will be used to lookup spatial reference systems in the spatial_ref_sys table.</P> <p>The SQLite database is essentially typeless, but the SQLite driver will attempt to classify attributes field as text, integer or floating point based on the contents of the first record in a table. None of the list attribute field types existing in SQLite.</p> <p>SQLite databases often due not work well over NFS, or some other networked file system protocols due to the poor support for locking. It is safest to operate only on SQLite files on a physical disk of the local system.</p> <p>SQLite is an optionally compiled in driver. It is not compiled in by default.</p> <p>While the SQLite driver supports reading spatial data from records, there is no support for spatial indexing, so spatial queries will tend to be slow. Attributes queries may be fast, especially if indexes are built for appropriate attribute columns using the "CREATE INDEX <indexname> ON <tablename> ( <columnname> )" SQL command.</p> <p>By default, SQL statements are passed directly to the SQLite database engine. It's also possible to request the driver to handle SQL commands with <a href="/ogr/ogr_sql.html">OGR SQL</a> engine, by passing <strong>"OGRSQL"</strong> string to the ExecuteSQL() method, as name of the SQL dialect.</p> <h2>Creation Issues</h2> <p>The SQLite driver supports creating new SQLite database files, or adding tables to existing ones. Note that a new database file cannot be created over an existing file.</p> <h3>Database Creation Options</h3> <ul> <li> <b>METADATA=yes/no</b>: This can be used to avoid creating the geometry_columns and spatial_ref_sys tables in a new database. By default these metadata tables are created when a new database is created. </ul> <h3>Layer Creation Options</h3> <ul> <li> <b>FORMAT=WKB/WKT</b>: Controls the format used for the geometry column. By default WKB (Well Known Binary) is used. This is generally more space and processing efficient, but harder to inspect or use in simple applications than WKT (Well Known Text). <li> <b>LAUNDER=yes/no</b>: Controls whether layer and field names will be laundered for easier use in SQLite. Laundered names will be convered to lower case and some special characters will be changed to underscores. </ul> <h2>Other Notes</h2> <ul> <li>Development of the OGR SQLite driver was supported by <a href="http://www.dmsolutions.ca/">DM Solutions Group</a> and <a href="http://www.gomoos.org/">GoMOOS</a>.</li> <li><a href="http://www.sqlite.org/">http://www.sqlite.org</a>: Main SQLite page.</li> <li> <A href="http://trac.osgeo.org/fdo/wiki/FDORfc16">FDO RFC 16</a>: FDO Provider for SQLite</li> </ul> </body> </html>
