假设有一个包含时间戳列的表,现在想将表按日期连续性进行分区。可以通过以下步骤实现:
首先将时间戳列转化为日期格式,使用DATE函数可以实现,如将2022-01-01 10:23:45转化为2022-01-01。
接下来使用LAG函数和DATEDIFF函数来计算相邻两行日期之间的天数差。如果相差1天,则将这两行放在同一个分区,否则放在不同的分区。
最后使用ROW_NUMBER OVER函数按照分区和日期排序,以保证结果的顺序正确。
代码示例如下:
SELECT timestamp, DATE(timestamp) AS date, DATEDIFF(DATE(timestamp), LAG(DATE(timestamp), 1) OVER(ORDER BY timestamp)) AS date_diff, ROW_NUMBER() OVER (PARTITION BY date_partition ORDER BY timestamp) AS row_number FROM my_table WINDOW date_partition AS (CASE WHEN date_diff = 1 OR date_diff IS NULL THEN 0 ELSE 1 END) + SUM(CASE WHEN date_diff = 1 OR date_diff IS NULL THEN 0 ELSE 1 END) OVER (ORDER BY timestamp)