Index: trunk/core/kernel/db/dbitem.php
===================================================================
diff -u -N -r7635 -r7855
--- trunk/core/kernel/db/dbitem.php	(.../dbitem.php)	(revision 7635)
+++ trunk/core/kernel/db/dbitem.php	(.../dbitem.php)	(revision 7855)
@@ -323,7 +323,7 @@
 	{
 		$skip = false;
 		$skip = $skip || ( isset($this->VirtualFields[$field_name]) ); //skipping 'virtual' field
-		$skip = $skip || ( !getArrayValue($this->FieldValues, $field_name) && getArrayValue($this->Fields[$field_name], 'skip_empty') ); //skipping 'virtual' field
+		$skip = $skip || ( !getArrayValue($this->FieldValues, $field_name) && getArrayValue($this->Fields[$field_name], 'skip_empty') ); //skipping marked field with 'skip_empty'
 //		$skip = $skip || ($field_name == $this->IDField && !$force_id); //skipping Primary Key
 
 //		$table_name = preg_replace("/^(.*)\./", "$1", $field_name);
@@ -538,8 +538,14 @@
 			array_push($unique_fields,$field);
 			foreach($unique_fields as $unique_field)
 			{
-				$where[] = '`'.$unique_field.'` = '.$this->Conn->qstr( $this->GetDBField($unique_field) );
+				// if field is not empty or if it is required - we add where condition
+				if ($this->GetDBField($unique_field) != '' || $this->Fields[$unique_field]['required']) {
+					$where[] = '`'.$unique_field.'` = '.$this->Conn->qstr( $this->GetDBField($unique_field) );
+				}
 			}
+			// This can ONLY happen if all unique fields are empty and not required.
+			// In such case we return true, because if unique field is not required there may be numerous empty values
+			if (!$where) return true;
 
 			$sql = 'SELECT COUNT(*) FROM %s WHERE ('.implode(') AND (',$where).') AND ('.$this->IDField.' <> '.(int)$this->ID.')';
 
@@ -669,38 +675,43 @@
 
 		$fields_sql = '';
 		$values_sql = '';
-		foreach ($this->FieldValues as $field_name => $field_value)
-		{
+		foreach ($this->FieldValues as $field_name => $field_value) {
 			if ($this->SkipField($field_name, $force_id)) continue;
 
-			$fields_sql .= sprintf('`%s`, ',$field_name); //Adding field name to fields block of Insert statement
-			//Adding field' value to Values block of Insert statement, escaping it with ADODB' qstr
-			if (is_null( $this->FieldValues[$field_name] ))
-			{
-				if (isset($this->Fields[$field_name]['not_null']) && $this->Fields[$field_name]['not_null'])
-				{
-	    			$values_sql .= $this->Conn->qstr($this->Fields[$field_name]['default']).', ';
-		    	}
-		    	else
-		    	{
-		    		$values_sql .= 'NULL, ';
-		    	}
-		    }
-		    else
-		    {
-		    	$values_sql .= sprintf('%s, ',$this->Conn->qstr($this->FieldValues[$field_name], 0));
-		    }
+			//Adding field' value to Values block of Insert statement, escaping it with qstr
+			if (is_null( $this->FieldValues[$field_name] )) {
+				if (isset($this->Fields[$field_name]['not_null']) && $this->Fields[$field_name]['not_null']) {
+					$values_sql .= $this->Conn->qstr($this->Fields[$field_name]['default'], 0);
+				}
+				else {
+					$values_sql .= 'NULL';
+				}
+			}
+			else {
+				if ($field_name == $this->IDField && $this->FieldValues[$field_name] == 0) {
+					$values_sql .= 'DEFAULT';
+				}
+				else {
+					$values_sql .= $this->Conn->qstr($this->FieldValues[$field_name], 0);
+				}
+			}
+
+			$fields_sql .= '`'.$field_name.'`, '; //Adding field name to fields block of Insert statement
+			$values_sql .= ', ';
 		}
 		//Cutting last commas and spaces
 		$fields_sql = ereg_replace(", $", '', $fields_sql);
 		$values_sql = ereg_replace(", $", '', $values_sql);
 		$sql = sprintf('INSERT INTO %s (%s) VALUES (%s)', $this->TableName, $fields_sql, $values_sql); //Formatting query
 
 		//Executing the query and checking the result
-		if($this->Conn->ChangeQuery($sql) === false) return false;
+		if ($this->Conn->ChangeQuery($sql) === false) return false;
 
 		$insert_id = $this->Conn->getInsertID();
-		if($insert_id == 0) $insert_id = $this->FieldValues[$this->IDField];
+		if ($insert_id == 0) {
+			// insert into temp table (id is not auto-increment field)
+			$insert_id = $this->FieldValues[$this->IDField];
+		}
 		$this->setID($insert_id);
 
 		if (!$system_create){