如何在Impala单查询中修改TRUNC()返回的一周起始日？

Absolutely feasible! You don’t need to tweak any cluster or server settings—you can adjust this logic directly within your query with a simple date arithmetic trick.

Here’s the modified query that will return the Sunday-starting week's first day for your target date:

SELECT DATE_ADD(TRUNC(DATE_ADD('2018-01-01', INTERVAL 1 DAY), 'D'), INTERVAL -1 DAY);

How this works: #

• First, we shift the original date forward by 1 day using DATE_ADD('2018-01-01', INTERVAL 1 DAY). This converts any Sunday to a Monday, aligning it with Impala’s default week start for the TRUNC('D') function.
• Next, TRUNC(..., 'D') gives us the Monday that starts the week containing the shifted date.
• Finally, we shift back by 1 day with DATE_ADD(..., INTERVAL -1 DAY) to get the corresponding Sunday, which becomes our desired week start.

Example test cases: #

• For '2018-01-01' (a Monday), this returns 2017-12-31 (the preceding Sunday, correct week start).
• For '2018-01-07' (a Sunday), this returns 2018-01-07 (the same day, since it’s the week start).
• For '2018-01-03' (a Wednesday), this returns 2017-12-31 (the Sunday before the week containing this Wednesday).

This approach is self-contained, works in a single query, and doesn’t rely on any global configuration changes.

内容的提问来源于stack exchange，提问作者Tony