computing z-scores

You construct a z-score for a set of values by subtracting the average from the value and dividing the result by the standard deviation. I know how to do this in a two-step procedure. First, I compute the average and standard deviation. In a second run I use the formula and apply it to each value. 

Is there a way of doing this in a single-step procedure or can you chain the two parts together in one query?  This goes beyond my SQL competence. 

Martin Mueller