Oracle Message PLS-00385 - type mismatch found at string in SELECT...INTO statement

ERRORtype mismatch found at string in SELECT...INTO statement
CAUSEThe expressions to the left and right of the INTO clause in a SELECT...INTO statement do not match in datatype, and it is unclear which implicit conversion is required to correct the mismatch.
ACTIONChange the expressions so that their datatypes match. You might want to use datatype conversion functions in the select list.