regex get string within two string - regex

Question

I have a query and want to get table names between from & where
If its a single line and single table without alias i could do so:
(?<=from )([^#]\w*)(?=.*where)
I need to get each table except the prefixed table. i.e course c marks s
But i can't figure out regex for the following Query.
(The where clause could be in same line or new line, on start of line or with space or tab)
from #prefix#student, course c, marks m
where ....
There are also sub queries in some places, if that case could also be handled would help.
select ... from course c
where id = (select ... from student where ...)
I'm trying to find & replace in sublime text 3 editor
Test case queries:
//output [course]
select ... from course
where ...
//output [course c] [marks s]
select ... from course c, marks s
where ....
//output [marks m]
select ... from #prefix#course c, marks m
where ...
//output [student s]
select ... from #prefix#course c
where id = (select ... from student s where ...)

Answer 1

You can use the following regex:
\bfrom\b(?!\s*#)([^w]*(?:\bw(?!here\b)[^w]*)*)\bwhere\b
See the regex demo
Check Case sensitive option in case you need that.
If you need to just highlight all between from and where, use lookarounds:
(?<=\bfrom\b)(?!\s*#)([^w]*(?:\bw(?!here\b)[^w]*)*)(?=\bwhere\b)
See another demo and the screen with results:
Regex breakdown:
(?<=\bfrom\b) - check if there is a whole word from before the next...
(?!\s*#) - make sure there is no 0 or more whitespaces followed by #
([^w]*(?:\bw(?!here\b)[^w]*)*) - match any text that is not where up to...
(?=\bwhere\b) - a whole word where.
UPDATE
Since you need to get comma-separated values excluding prefixed names with their aliases, you need a boundary-constrained regex. It can be achieved with \G operator:
(?:\bfrom\b(?:\s*#\w+(?:\s*\w+))*+|(?!^)\G),?\s*\K(?!(?:\w+ )?\bwhere\b)([\w ]+)(?=[^w]*(?:\bw(?!here\b)[^w]*)*\bwhere\b)
Here,
(?:\bfrom\b(?:\s*#\w+(?:\s*\w+))*+|(?!^)\G) - matches from (as a whole word) followed by optional whitespace followed by # and 1 or more alphanumerics that are followed by whitespaces+alphanumerics (alias)
,?\s*\K - optional (1 or 0) commas followed by 0 or more whitespaces that are followed by \K that forces the engine to omit the whole chunk of text matched so fat
(?!(?:\w+ )?\bwhere\b) - a restrictive lookahead with which we forbid the next or the word following the next word to be equal to where
([\w ]+) - our match, 1 or more alphanumerics or space (may be replaced with [\w\h]+)
(?=[^w]*(?:\bw(?!here\b)[^w]*)*\bwhere\b) - a trailing boundary: there must be text other than where up to the first where.