You can use the NOT logical operator in combination with any SAS and WHERE expression operator. And you can combine the NOT operator with AND and OR. For example: where skill not eq 'cobol' or years ...

The AND logical operator (&) compares two matrices, element by element, to produce a new matrix. An element of the new matrix is 1 if the corresponding elements of matrix1 and matrix2 are both nonzero ...

Boolean operators, which Excel calls logical functions, include AND, OR, NOT, and a new function called XOR. These operators are used between search terms to narrow, expand, ...