Question

What is the string concatenation operator in Oracle SQL?

Are there any ‘interesting’ features I should be careful of?

(This seems obvious, but I couldn’t find a previous question asking it).

Answer 1

It is ||, for example:

select 'Mr ' || ename from emp; 

The only ‘interesting’ feature I can think of is that 'x' || null returns 'x', not null as you might perhaps expect.