Note An empty result set is not the same as a null value. For a scrollable cursor, all the rows in the result set are returned to the calling batch, procedure, or trigger when the procedure exits. When returned, the cursor position is left at the position of the last fetch executed in the procedure.
The wall sit strengthens your lower body. Your quadriceps on the fronts of your upper legs remain in a static contraction to support the wall sit. The hamstrings on the backs of your upper legs also remain contracted as you sit. Your glutes contract during the wall sit to keep your body stable and balanced.
The gluteus maximus is attached to the coccyx as well as to other bones. A spasm or tightness of this muscle can pull on the coccyx and cause pain when you move into a sitting position or raise yourself. It doesn't cause pain while you are sitting. The spasm, and the pain, is normally just on one side.