"No Root Node! Parsing Failed?" error when re-coding some text using QGIS Field Calculator

Question

I am attempting to re-code some text data in the attribute table using the QGIS Field Calculator tool, but I keep getting an error message:

An Error occured while evaluating the calculation string: "No Root Node! Parsing Failed?

I am using the expressions bar, this is happening while in editing mode.

Answer 1

It is necessary to enclose the string value you wish to calculate in single quotes like this: 'SAMPLE TEXT'