Grouping employees into salary bands on the fly

Question

Accepted Answer

CASE can appear in GROUP BY just like any other expression. Alice (95000) -> Senior, Bob (65000) -> Junior, Carol (80000) -> Senior. GROUP BY collapses by the CASE result: Senior group has Alice and Carol (count=2), Junior group has Bob (count=1). Some databases let you reference the SELECT alias in GROUP BY (GROUP BY band), but the standard-compliant form repeats the expression.