anchor.diff:                        | <limit_clause>
                         | <group_by_clause>
                         | <distinct_clause>
  +                      | <execute_clause>
                         | <browse_by_clause>
                         | <fetching_stored_clause>
                         | <route_by_clause>
  
positive.code: 
  <distinct_clause> ::= DISTINCT <distinct_spec>
  
  <group_spec> ::= <or_column_name_list> [TOP <max_per_group>]
  
  <distinct_spec> ::= <or_column_name_list>
  
  <or_column_name_list> ::= <column_name> ( OR <column_name> )*
  
  <limit_clause> ::= LIMIT [<offset> ','] <count>
  
  
negative.code: 
  <describe_stmt> ::= ( DESC | DESCRIBE ) [<index_name>]
  
  <select_list> ::= '*' | (<column_name>|<aggregation_function>)( ',' <column_name>|<aggregation_function> )*
  
  <column_name_list> ::= <column_name> ( ',' <column_name> )*
  
  <aggregation_function> ::= <function_name> '(' <column_name> ')'
  
  <function_name> ::= <column_name>
  
  <from_clause> ::= FROM <index_name>
  
  