anchor.diff:      : (tableName | alias)? columnName (ASC | DESC)?
       ;
   
  +createIndexDefinitionClause_
  +    : tableIndexClause_ | bitmapJoinIndexClause_
  +    ;
  +
   tableAlias
       : tableName alias? (COMMA_ tableName alias?)*
       ;
   
  -alterClause_
  +alterDefinitionClause_
       : (alterTableProperties | columnClauses | constraintClauses | alterExternalTable)?
       ;
   
  
positive.code:     : (columnName | attributeName) (DEFAULT expr)? (inlineConstraint* | inlineRefConstraint?) | outOfLineConstraint | outOfLineRefConstraint
      ;
  
  
  
negative.code:     ;
  
  createIndex
      : CREATE createIndexSpecification_ INDEX indexName ON createIndexDefinitionClause_
      ;
  
  alterTable
      : ALTER TABLE tableName alterDefinitionClause_
      ;
  
  // TODO hongjun throw exeption when alter index on oracle
  alterIndex
      : ALTER INDEX indexName renameIndexClause_
      ;
  
  dropTable
  