题解|存疑不去重？高质量的回答中用户属于各级别的数量#

## 高质量回答中属于各级别的数量
SELECt (CASE WHEN author_level in (5,6) THEN '5-6级'
             WHEN author_level in (3,4) THEN '3-4级'
             ELSE '1-2级' END ) AS level_cnt, COUNT(a.author_id) AS num
FROM answer_tb a
LEFT JOIN author_tb b
ON a.author_id = b.author_id
WHERE char_len >= 100
GROUP BY level_cnt
ORDER BY num DESC