| NULL | 未知 / 未发生 |
|---|---|
| 0 | 发生了且为零 |
| 影响 | avg、占比、非空率 |
区分统计
区分统计
SELECT
count(1) AS rows_all,
sum(CASE WHEN amt IS NULL THEN 1 ELSE 0 END) AS rows_null,
sum(CASE WHEN amt = 0 THEN 1 ELSE 0 END) AS rows_zero,
avg(amt) AS avg_non_null
FROM dwd_order;聚合函数忽略 NULL，报表把 NULL 显示为 0 时要谨慎，可能掩盖缺失。