Regex - capture word(s) before and then capture word after the match

Question

5.00/5 (1 vote)

See more:

It seems as if it ought to be simple, but I've spent 4 hours reading the Espresso tutorial and trying various expresions without success. Regex just seems to be a language I don't understand

Need to document a LARGE number of SQL Select statements where data from one system is being SELECTed and INSERTed into another. In many cases the lines are of the form

columnX as columnY

and in other cases they are

CASE WHEN...as columnZ

So, the word "AS" is common in the lines and I need to show the map columnX to columnY or [expression] to columnZ by separately capturing the word(s) before the AS and the word after the AS

Posted 3-Sep-10 2:19am

Duke Carey

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Duke Carey · Accepted Answer · 2010-09-03T03:54:00

Solution 1

Figured it out: (.*)(?:\bas\b)(.*)

Posted 3-Sep-10 3:54am

Duke Carey

Comments

TheyCallMeMrJames 3-Sep-10 10:02am

good work, mate. cheers.

TheyCallMeMrJames · Accepted Answer · 2010-09-03T04:00:00

Regex is sexy. It's also a time-pig as you can get to invest a lot of time in an otherwise trivial task. I've gotten lost trying to code some really beautiful things in regex.

That said, why not try this? Read all lines of the file into a string array, then do something like this:

C#

string[] lines = File.ReadAllLines("yourfile");
var mappingLines = from l in lines
                   where l.Contains(" as ")
                   select l;
foreach (var line in mappingLines)
{
    string[] map = line.Split(" as ".ToCharArray());
}

The first bit filters you down to only the lines with " as " in them, giving you your maps. The second bit is just a simple string split.

You might need to work a little on the map after the split to pull out the CASE WHEN, but that would get you started. I'd need more info on that text pattern to help more.

Cheers.