Question

Problem that i face:

-I have an input string, a SQL statement that i need to parse

-extract the value that need to be insert base on the column name specify

-i can extract the value that is wrap in between 2 single quotes, but:

–?what about value that has no single quotes wrap at them? (like: integer or double)

–?what if the value inside already has single quotes? (like: ‘James”s dictionary’)

Below is the sample input string:

INSERT INTO LJS1_DX (base, doc, key1, key2, no, sq, eq, ln, en, date, line) 
VALUES ('GET','','#000210','','   0','   1','5',1,0,'20100706','Street''James''s dictionary')

The Java Code i have below match value between two single quotes only:

 Pattern p = Pattern.compile("'.*?'");
 columnValues = "'GET0','','#000210','','   0','   1','5',1,0,'20100706','Street''James''s dictionary'";
 Matcher m = p.matcher(columnValues); // get a matcher object
 StringBuffer output = new StringBuffer();
 while (m.find()) {
  logger.trace(m.group());
 }

Appreciate if anyone can provide any guideline or sample to this question.

Thank you!!

Answer 1

I agree with gnibbler that this is a job for a csv parser.

A regex that works on your example would be

'(?:''|[^'])*'|[^',]+

which looks challenging to debug and maintain, doesn’t it?

Explanation:

'            # First alternative: match an "opening" '
 (?:         # followed by either...
  ''         # two ' in a row (escaped ')
 |           # or...
  [^']       # any character that is not a '
 )*          # zero or more times,
'            # then match a "closing" '
|            # or (second alternative):
[^',\s]+     # match any run of characters except ', comma or whitespace

It also works if there is whitespace around the values/commas (and will leave that out of the match).