Index: src/providers/spatialite/qgsspatialiteprovider.cpp
===================================================================
--- src/providers/spatialite/qgsspatialiteprovider.cpp	(revision 14418)
+++ src/providers/spatialite/qgsspatialiteprovider.cpp	(working copy)
@@ -52,6 +52,8 @@
   mGeometryColumn = anUri.geometryColumn();
   mSqlitePath = anUri.database();
   mSubsetString = anUri.sql();
+  mPrimaryKey = anUri.keyColumn();
+  mQuery = mTableName;
 
   // trying to open the SQLite DB
   spatialite_init( 0 );
@@ -131,6 +133,7 @@
 {
   int ret;
   int i;
+  sqlite3_stmt *stmt = NULL;
   char **results;
   int rows;
   int columns;
@@ -138,11 +141,15 @@
   QString pkName;
   int pkCount = 0;
   int fldNo = 0;
+  QString sql;
 
   attributeFields.clear();
+
+  if ( !isQuery )
+  {
   mPrimaryKey.clear();
 
-  QString sql = QString( "PRAGMA table_info(\"%1\")" ).arg( mTableName );
+    sql = QString( "PRAGMA table_info(%1)" ).arg( quotedIdentifier( mTableName ) );
 
   ret = sqlite3_get_table( sqliteHandle, sql.toUtf8().constData(), &results, &rows, &columns, &errMsg );
   if ( ret != SQLITE_OK )
@@ -190,7 +197,74 @@
     }
   }
   sqlite3_free_table( results );
+  }
+  else
+  {
+    sql = QString( "select * from %1 limit 1" ).arg( mQuery );
 
+    if ( sqlite3_prepare_v2( sqliteHandle, sql.toUtf8().constData(), -1, &stmt, NULL ) != SQLITE_OK )
+    {
+      // some error occurred
+      QgsDebugMsg( QString( "SQLite error: %1\n\nSQL: %2" )
+                   .arg( sql )
+                   .arg( QString::fromUtf8( sqlite3_errmsg( sqliteHandle ) ) ) );
+      return;
+    }
+
+    ret = sqlite3_step( stmt );
+    if ( ret == SQLITE_DONE )
+    {
+      // there are no rows to fetch
+      sqlite3_finalize( stmt );
+      return;
+    }
+
+    if ( ret == SQLITE_ROW )
+    {
+      // one valid row has been fetched from the result set
+      columns = sqlite3_column_count( stmt );
+      for ( i = 0; i < columns; i++ )
+      {
+        QString name = QString::fromUtf8( sqlite3_column_name( stmt, i ) );
+        const char *type = sqlite3_column_decltype( stmt, i );
+        if ( type == NULL )
+            type = "TEXT";
+
+        if ( name != mPrimaryKey )
+        {
+          pkCount++;
+          pkName = name;
+        }
+
+        if ( name != mGeometryColumn )
+        {
+          // for sure any SQLite value can be represented as SQLITE_TEXT
+          QVariant::Type fieldType = QVariant::String;
+
+          // making some assumptions in order to guess a more realistic type
+          if ( strcasecmp( type, "int" ) == 0 ||
+               strcasecmp( type, "integer" ) == 0 ||
+               strcasecmp( type, "bigint" ) == 0 ||
+               strcasecmp( type, "smallint" ) == 0 ||
+               strcasecmp( type, "tinyint" ) == 0 ||
+               strcasecmp( type, "boolean" ) == 0 )
+          {
+            fieldType = QVariant::Int;
+          }
+          else if ( strcasecmp( type, "real" ) == 0 ||
+                    strcasecmp( type, "double" ) == 0 ||
+                    strcasecmp( type, "double precision" ) == 0 || strcasecmp( type, "float" ) == 0 )
+          {
+            fieldType = QVariant::Double;
+          }
+
+          attributeFields.insert( fldNo++, QgsField( name, fieldType, type, 0, 0, "" ) );
+        }
+      }
+    }
+    sqlite3_finalize( stmt );
+  }
+
   if ( pkCount == 1 )
   {
     // setting the Primary Key column name
@@ -221,7 +295,9 @@
 
   feature.setValid( false );
 
-  QString sql = "SELECT ROWID";
+  QString primaryKey = !isQuery ? "ROWID" : quotedIdentifier( mPrimaryKey );
+
+  QString sql = QString( "SELECT %1" ).arg( primaryKey );
   for ( QgsAttributeList::const_iterator it = fetchAttributes.constBegin(); it != fetchAttributes.constEnd(); ++it )
   {
     const QgsField & fld = field( *it );
@@ -232,7 +308,10 @@
   {
     sql += QString( ", AsBinary(%1)" ).arg( quotedIdentifier( mGeometryColumn ) );
   }
-  sql += QString( " FROM %1 WHERE ROWID = %2" ).arg( quotedIdentifier( mTableName ) ).arg( featureId );
+  sql += QString( " FROM %1 WHERE %2 = %3" )
+         .arg( mQuery )
+         .arg( primaryKey )
+         .arg( featureId );
 
   if ( sqlite3_prepare_v2( sqliteHandle, sql.toUtf8().constData(), -1, &stmt, NULL ) != SQLITE_OK )
   {
@@ -267,7 +346,7 @@
     {
       if ( ic == 0 )
       {
-        // first column always contains the ROWID
+        // first column always contains the ROWID (or the primary key)
         feature.setFeatureId( sqlite3_column_int( stmt, ic ) );
       }
       else
@@ -391,7 +470,7 @@
     {
       if ( ic == 0 )
       {
-        // first column always contains the ROWID
+        // first column always contains the ROWID (or the primary key)
         feature.setFeatureId( sqlite3_column_int( sqliteStatement, ic ) );
       }
       else
@@ -522,7 +601,9 @@
     sqliteStatement = NULL;
   }
 
-  QString sql = "SELECT ROWID";
+  QString primaryKey = !isQuery ? "ROWID" : quotedIdentifier( mPrimaryKey );
+
+  QString sql = QString( "SELECT %1" ).arg( primaryKey );
   for ( QgsAttributeList::const_iterator it = fetchAttributes.constBegin(); it != fetchAttributes.constEnd(); ++it )
   {
     const QgsField & fld = field( *it );
@@ -533,7 +614,7 @@
   {
     sql += QString( ", AsBinary(%1)" ).arg( quotedIdentifier( mGeometryColumn ) );
   }
-  sql += QString( " FROM %1" ).arg( quotedIdentifier( mTableName ) );
+  sql += QString( " FROM %1" ).arg( mQuery );
 
   QString whereClause;
 
@@ -569,7 +650,10 @@
         mbrFilter += QString( "ymin <= %1 AND " ).arg( QString::number( rect.yMaximum(), 'f', 6 ) );
         mbrFilter += QString( "ymax >= %1" ).arg( QString::number( rect.yMinimum(), 'f', 6 ) );
         QString idxName = QString( "idx_%1_%2" ).arg( mIndexTable ).arg( mIndexGeometry );
-        whereClause += QString( "ROWID IN (SELECT pkid FROM %1 WHERE %2)" ).arg( quotedIdentifier( idxName ) ).arg( mbrFilter );
+        whereClause += QString( "%1 IN (SELECT pkid FROM %2 WHERE %3)" )
+                       .arg( quotedIdentifier( primaryKey ) )
+                       .arg( quotedIdentifier( idxName ) )
+                       .arg( mbrFilter );
       }
       else if ( spatialIndexMbrCache )
       {
@@ -579,7 +663,10 @@
                       arg( QString::number( rect.yMinimum(), 'f', 6 ) ).
                       arg( QString::number( rect.xMaximum(), 'f', 6 ) ).arg( QString::number( rect.yMaximum(), 'f', 6 ) );
         QString idxName = QString( "cache_%1_%2" ).arg( mIndexTable ).arg( mIndexGeometry );
-        whereClause += QString( "ROWID IN (SELECT rowid FROM %1 WHERE mbr = FilterMbrIntersects(%2))" ).arg( quotedIdentifier( idxName ) ).arg( mbr );
+        whereClause += QString( "%1 IN (SELECT rowid FROM %2 WHERE mbr = FilterMbrIntersects(%3))" )
+                       .arg( quotedIdentifier( primaryKey ) )
+                       .arg( quotedIdentifier( idxName ) )
+                       .arg( mbr );
       }
       else
       {
@@ -711,7 +798,7 @@
   // get the field name
   const QgsField & fld = field( index );
 
-  QString sql = QString( "SELECT Min(\"%1\") FROM \"%2\"" ).arg( fld.name() ).arg( mTableName );
+  QString sql = QString( "SELECT Min(%1) FROM %2" ).arg( quotedIdentifier( fld.name() ) ).arg( mQuery );
 
   if ( !mSubsetString.isEmpty() )
   {
@@ -766,7 +853,7 @@
   // get the field name
   const QgsField & fld = field( index );
 
-  QString sql = QString( "SELECT Max(\"%1\") FROM \"%2\"" ).arg( fld.name() ).arg( mTableName );
+  QString sql = QString( "SELECT Max(%1) FROM %2" ).arg( quotedIdentifier( fld.name() ) ).arg( mQuery );
 
   if ( !mSubsetString.isEmpty() )
   {
@@ -819,7 +906,7 @@
   // get the field name
   const QgsField & fld = field( index );
 
-  sql = QString( "SELECT DISTINCT \"%1\" FROM \"%2\" ORDER BY \"%1\"" ).arg( fld.name() ).arg( mTableName );
+  sql = QString( "SELECT DISTINCT %1 FROM %2 ORDER BY %1" ).arg( quotedIdentifier( fld.name() ) ).arg( mQuery );
 
   if ( !mSubsetString.isEmpty() )
   {
@@ -1511,6 +1598,7 @@
   mTableBased = false;
   mViewBased = false;
   mVShapeBased = false;
+  isQuery = false;
 
 // checking if this one is a Table-based layer
   QString sql = QString( "SELECT read_only FROM geometry_columns "
@@ -1594,6 +1682,49 @@
   }
   sqlite3_free_table( results );
 
+  // checking if this one is a select query
+  if ( mQuery.startsWith( "(select", Qt::CaseInsensitive ) &&
+       mQuery.endsWith( ")" ) )
+  {
+    // get a new alias for the subquery
+    int index = 0;
+    QString alias;
+    QRegExp regex;
+    do
+    {
+      alias = QString( "subQuery_%1" ).arg( QString::number( index++ ) );
+      QString pattern = QString( "(\\\"?)%1\\1" ).arg( QRegExp::escape( alias ) );
+      regex.setPattern( pattern );
+      regex.setCaseSensitivity( Qt::CaseInsensitive );
+    }
+    while ( mQuery.contains( regex ) );
+
+    // convert the custom query into a subquery
+    mQuery = QString( "%1 as %2" )
+             .arg( mQuery )
+             .arg( quotedIdentifier( alias ) );
+
+    sql = QString( "SELECT 0 FROM %1 LIMIT 1" ).arg( mQuery );
+    ret = sqlite3_get_table( sqliteHandle, sql.toUtf8().constData(), &results, &rows, &columns, &errMsg );
+    if ( ret == SQLITE_OK && rows == 1 )
+    {
+      isQuery = true;
+      mReadOnly = true;
+      count++;
+    }
+    if ( errMsg )
+    {
+      QgsDebugMsg( QString( "sqlite error %1 [%2]" ).arg( sql ).arg( errMsg ) );
+      sqlite3_free( errMsg );
+      errMsg = 0;
+    }
+    sqlite3_free_table( results );
+  }
+  else
+  {
+    mQuery = quotedIdentifier( mTableName );
+  }
+
 // checking for validity
   return count == 1;
 }
@@ -1607,6 +1738,8 @@
     ret = getViewGeometryDetails();
   if ( mVShapeBased )
     ret = getVShapeGeometryDetails();
+  if ( isQuery )
+    ret = getQueryGeometryDetails();
   return ret;
 }
 
@@ -1845,6 +1978,122 @@
   return false;
 }
 
+bool QgsSpatiaLiteProvider::getQueryGeometryDetails()
+{
+  int ret;
+  int i;
+  char **results;
+  int rows;
+  int columns;
+  char *errMsg = NULL;
+
+  QString fType( "" );
+  QString xSrid( "" );
+
+  // get stuff from the relevant column instead. This may (will?)
+  // fail if there is no data in the relevant table.
+  QString sql = QString( "select srid(%1), geometrytype(%1) from %2" )
+        .arg( quotedIdentifier( mGeometryColumn ) )
+        .arg( mQuery );
+
+  //it is possible that the where clause restricts the feature type
+  if ( !mSubsetString.isEmpty() )
+  {
+    sql += " WHERE " + mSubsetString;
+  }
+
+  sql += " limit 1";
+
+  ret = sqlite3_get_table( sqliteHandle, sql.toUtf8().constData(), &results, &rows, &columns, &errMsg );
+  if ( ret != SQLITE_OK )
+    goto error;
+  if ( rows < 1 )
+    ;
+  else
+  {
+    for ( i = 1; i <= rows; i++ )
+    {
+      xSrid = results[( i * columns ) + 0];
+      fType = results[( i * columns ) + 1];
+    }
+  }
+  sqlite3_free_table( results );
+
+  if ( !xSrid.isEmpty() && !fType.isEmpty() )
+  {
+    if ( fType == "GEOMETRY" )
+    {
+      // check to see if there is a unique geometry type
+      sql = QString( "select distinct "
+                     "case"
+                     " when geometrytype(%1) IN ('POINT','MULTIPOINT') THEN 'POINT'"
+                     " when geometrytype(%1) IN ('LINESTRING','MULTILINESTRING') THEN 'LINESTRING'"
+                     " when geometrytype(%1) IN ('POLYGON','MULTIPOLYGON') THEN 'POLYGON'"
+                     " end "
+                     "from %2" )
+            .arg( quotedIdentifier( mGeometryColumn ) )
+            .arg( mQuery );
+
+      if ( !mSubsetString.isEmpty() )
+        sql += " where " + mSubsetString;
+
+      ret = sqlite3_get_table( sqliteHandle, sql.toUtf8().constData(), &results, &rows, &columns, &errMsg );
+      if ( ret != SQLITE_OK )
+        goto error;
+      if ( rows != 1 )
+        ;
+      else
+      {
+        for ( i = 1; i <= rows; i++ )
+        {
+          fType = results[( 1 * columns ) + 0];
+        }
+      }
+      sqlite3_free_table( results );
+    }
+
+    if ( fType == "POINT" )
+    {
+      geomType = QGis::WKBPoint;
+    }
+    else if ( fType == "MULTIPOINT" )
+    {
+      geomType = QGis::WKBMultiPoint;
+    }
+    else if ( fType == "LINESTRING" )
+    {
+      geomType = QGis::WKBLineString;
+    }
+    else if ( fType == "MULTILINESTRING" )
+    {
+      geomType = QGis::WKBMultiLineString;
+    }
+    else if ( fType == "POLYGON" )
+    {
+      geomType = QGis::WKBPolygon;
+    }
+    else if ( fType == "MULTIPOLYGON" )
+    {
+      geomType = QGis::WKBMultiPolygon;
+    }
+    mSrid = xSrid.toInt();
+  }
+
+  if ( geomType == QGis::WKBUnknown || mSrid < 0 )
+    goto error;
+
+  return getSridDetails();
+
+error:
+  // unexpected error
+  if ( errMsg != NULL )
+  {
+    QgsDebugMsg( QString( "SQL error: %1\n\n%2" ).arg( sql ).arg( errMsg ? QString::fromUtf8( errMsg ) : "unknown cause" ) );
+    sqlite3_free( errMsg );
+  }
+  return false;
+}
+
 bool QgsSpatiaLiteProvider::getSridDetails()
 {
   int ret;
@@ -1891,8 +2140,10 @@
   int columns;
   char *errMsg = NULL;
 
-  QString sql = QString( "SELECT Min(MbrMinX(\"%1\")), Min(MbrMinY(\"%1\")), "
-                         "Max(MbrMaxX(\"%1\")), Max(MbrMaxY(\"%1\")), Count(*) " "FROM \"%2\"" ).arg( mGeometryColumn ).arg( mTableName );
+  QString sql = QString( "SELECT Min(MbrMinX(%1)), Min(MbrMinY(%1)), "
+                         "Max(MbrMaxX(%1)), Max(MbrMaxY(%1)), Count(*) " "FROM %2" )
+                .arg( quotedIdentifier( mGeometryColumn ) )
+                .arg( mQuery );
 
   if ( !mSubsetString.isEmpty() )
   {
Index: src/providers/spatialite/qgsspatialiteprovider.h
===================================================================
--- src/providers/spatialite/qgsspatialiteprovider.h	(revision 14418)
+++ src/providers/spatialite/qgsspatialiteprovider.h	(working copy)
@@ -266,6 +266,10 @@
        */
     bool valid;
     /**
+       * Flag indicating if the layer data source is based on a query
+       */
+    bool isQuery;
+    /**
        * Flag indicating if the layer data source is based on a plain Table
        */
     bool mTableBased;
@@ -290,6 +294,10 @@
      */
     QString mTableName;
     /**
+     * Name of the table or subquery
+     */
+    QString mQuery;
+    /**
        * Name of the primary key column in the table
        */
     QString mPrimaryKey;
@@ -363,6 +371,7 @@
     bool getTableGeometryDetails();
     bool getViewGeometryDetails();
     bool getVShapeGeometryDetails();
+    bool getQueryGeometryDetails();
     bool getSridDetails();
     bool getTableSummary();