Palindromes In SQL

Lukas Eder rises to a challenge:

SQL is a really cool language. I can write really complex business logic with this logic programming language. I was again thrilled about SQL recently, at a customer site:

Writing some nifty SQL queries for a customer. Wondering why anyone would even consider using a 3GL for any business logic at all??

— Lukas Eder (@lukaseder) August 21, 2017

But whenever I tweet something like the above, the inevitable happened. I was nerd sniped. Oleg Šelajev from ZeroTurnaround challenged me to prove that SQL is so awesome:

You have a String s (of length N), find all (i; j), i < j, such that s[i:j] is a palindrome. For bonus points, do it in O(n) or O(n*log(n))

— Oleg Šelajev (@shelajev) August 21, 2017

Given a string, find all substrings from that string, which are palindromes. Challenge accepted! (For the moment, let’s forget about algorithmic complexity.)

His answer is in Postgres syntax, and a commenter includes Oracle syntax.  T-SQL is left as an exercise for the reader.