1. sum()
SUM(show_cnt) OVER (ORDER BY show_cnt DESC) AS acc_show_cnt, --逐行累计
SUM(show_cnt) OVER () AS total_show_cnt--全部累计
2. sql提取中文，并计算字符长度
length(regexp_replace(title, '[^\u4e00-\u9fa5]', '')) AS chinese_chars_count
3. 想要把30行的结果sum起来
SUM(cnt) OVER (
ORDER BY
dt ROWS BETWEEN 29 PRECEDING
AND CURRENT ROW
) AS cnt_sum
