Using Regular Expressions to Parse SQL

Reedick, Andrew jr9445 at ATT.COM
Tue Feb 5 16:28:23 CET 2008


> -----Original Message-----
> From: python-list-bounces+jr9445=att.com at python.org [mailto:python-
> list-bounces+jr9445=att.com at python.org] On Behalf Of ct60 at aol.com
> Sent: Tuesday, February 05, 2008 9:31 AM
> To: python-list at python.org
> Subject: Using Regular Expressions to Parse SQL
> 
> 
> My pattern does not even come close.
> 
> Any help would be greatly appreciated.  My goal is to analyse a large
> number of SQL querys to try to identify the join field and see where
> indexing might make sense.
> 
> While I am mostly interested in understanding regular expressions, I
> would also be interested in knowing about any Python SQL parsers out
> there.


Python's regexes are a tad odd compared to Perl (or Perl's regexes are
odd.  Relativity.)  You need re.DOTALL to handle newlines in the sql:
	DOTALL
	Make the "." special character match any character at all,
including a newline; without this flag, "." will match anything except a
newline.
 


import re

s= ''' FROM ((qry_Scores_Lookup1 INNER JOIN CSS_Rpt1 ON
(qry_Scores_Lookup1.desc = CSS_Rpt1.desc) AND
(qry_Scores_Lookup1.lastcdu = CSS_Rpt1.lastcdu))'''

pat =
r"(^|\s+)FROM\s.+\s(?:INNER|LEFT|RIGHT)\s+JOIN\s.+\sON\s+((\s*(?:\S+)\s*
=\s*(?:\S+))(?:\s+|\s+AND\s+|$))+"
m = re.compile(pat, re.DOTALL).match(s)
if m:
	print m


('(qry_Scores_Lookup1.desc = CSS_Rpt1.desc) ', '(qry_Scores_Lookup1.desc
= CSS_Rpt1.desc)')


You should be able to tweak the regex to get the exact matches you want.

An alternative to writing a lengthy regex might be to just grab
everything after the ON and then string split on "AND".



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