token        ::= insert
               | select
               | meta-command
               | int
               | string
               | end-of-file

insert       ::= "insert"
select       ::= "select"

meta-command ::= "." "exit"

int          ::= sign? digit+
sign         ::= "+"
               | "-"
digit        ::= "0"
               | "1"
               | "2"
               | "3"
               | "4"
               | "5"
               | "6"
               | "7"
               | "8"
               | "9"

string       ::= '"' string-char* '"'
string-char  ::= '\' utf8-char
               | utf8-char-not-dbl-quote