12-13-2016 04:31 AM - edited 12-13-2016 04:43 AM
Single quotes prevent the resolution of macro triggers (& and %) in the enclosed text.
Exception: when single quotes are embedded within double quotes:
%let test=xxx; data test; test1 = "'&test'"; run;
12-13-2016 10:41 AM
Also the use of single quotes around a character literal also allows placing a single (or odd number of) double quote into the value such as the use of " for inch measurements: '5.3"' <= that is " followed with ' and vice versa "John's car". While possible to do with just one quote style the alternate 'John''s car' <= the '' is two single quotes, isn't quite as obvious in some situations and can be difficult to deal with for multiple single quotes needed within a single string.