Capture a dot with postgres regexp

Question

I have these strings :

3           FD160497.   2016  abcd
3           FD160497   2016  abcd

I want to capture \"FD\", the digits, then the do

Answer 1

The first lazy pattern made all quantifiers in the current branch lazy, so your pattern became equivalent to

.*?(FD)([0-9]{6})(\.)??.*?
                     ^^  ^

See its demo at regex101.com

See the 9.7.3.1. Regular Expression Details excerpt:

...matching is done in such a way that the branch, or whole RE, matches the longest or shortest possible substring as a whole. Once the length of the entire match is determined, the part of it that matches any particular subexpression is determined on the basis of the greediness attribute of that subexpression, with subexpressions starting earlier in the RE taking priority over ones starting later.

You need to use quantifiers consistently within one branch:

regexp_matches(string, '.*(FD)([0-9]{6})(\.)?.*') as sqn

or

regexp_matches(string, '.*[[:blank:]](FD)([0-9]{6})(\.)?.*') as sqn

See the regex demo