请教一条SQL语句怎么写

Answer 1

我用的是Oracle数据库：SELECT   AGE_SECTION, COUNT (1)
    FROM (SELECT CASE
                    WHEN AGE >= 20 AND AGE < 40
                       THEN '20-40'
                    WHEN AGE >= 40 AND AGE < 50
                       THEN '40-50'
                    WHEN AGE >= 50
                       THEN '>=50'
                 END AGE_SECTION
            FROM KS)
GROUP BY AGE_SECTION