Writing degrees Celsius in short hand ('c) in QGIS expression

Question

There is a way to add something before the ' to indicate to QGIS that it is a string and not a column. In expression builder I simply want

"temperature" || ''C'

Answer 1

You are almost there. However, you need one extra backslash \. It is used to escape any special character.

"temperature" || '\'C'

Another option can be achieved via:

concat("temperature", char(39), 'C')

where char(39) - is the Apostrophe in Unicode.