.count(*)与group by的统计问题

sql统计示例：

统计 group by 后每个分组的个数：

SELECT COUNT(*) FROM search_word GROUP BY word;

那么得到的结果是:

COUNT(*)
1
10
1
2
1
1
1
15

统计 group by 后分组个数

SELECT COUNT(DISTINCT word) FROM search_word;

结果：

COUNT(DISTINCT word)
346

或

SELECT COUNT(*) FROM (SELECT COUNT(*) FROM search_word GROUP BY word) t;

结果：

COUNT(*)
346