| 稠密 | 每日一实体一行 |
|---|---|
| 稀疏 | 变化日才落行 |
| 填充 | 窗口函数向前取最近值 |
稀疏向前填充
稀疏向前填充
SELECT dt, account_id,
last_value(balance, true) OVER (
PARTITION BY account_id ORDER BY dt
ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS balance
FROM fact_balance_sparse;稠密便于对比与关联；稀疏适合实体多、变化少的场景（如设备配置）。