Assign a value to a variable in a "SELECT" statement:SELECT @fruit1, @fruit2, @fruit3, @fruit4:='mango';You must use ":=" if you are assigning a value to a variable in any other type of statement ...

Prior to C++11 the .real() and .imag() methods were specified to return non-reference values, so it was a non-standard extension that allowed you to assign to the results of these methods ...