add tests

left factor parsing code

implement pretty printer

reimplement the fixity thing natively

dialect switching

fix lexing wrt suffixes

position annotation

emacs parse error formatting

haddock

= sql support

count(*)
decimal literals, split string and number literals
order by directions
distinct/all
limit,offset, top

scalar function syntax:
  aggregate app
  window app
  cast
  exists, in subquery
  scalar subquery
  in list
  any/some/all
  between
  is null/ is not null
  review all ansi sql operators
  interval literal
  typed string lit?
  placeholder/positional arg

other missing operators
  unary + -
  row constructors?
  extract
  substring

except, intersect, union


review identifiers
order by nulls first/last
extend case
more dots in identifiers
escapes in string literals
full number literals
quoted identifiers
group by (), grouping sets(), cube, rollup
lateral
corresponding
named windows
cte
apply, pivot
full tableref aliases
collate

within group aggregate syntax
try to do full review of sql2003 query syntax

maybe later: other dml