現在時刻

select getdate();

timestamp
---------------------
2008-12-04 16:10:43

SELECT CURRENT_DATETIME() as now;

+----------------------------+
| now                        |
+----------------------------+
| 2016-05-19T10:38:47.046465 |
+----------------------------+

truncate date

-- Redshift --
SELECT DATE_TRUNC('hour', TIMESTAMP '20200430 04:05:06.789');

date_trunc
2020-04-30 04:00:00

-- BigQuery --
SELECT DATETIME_TRUNC(DATETIME "2008-12-25 15:30:00", DAY) as truncated;

+------------------------+
| truncated              |
+------------------------+
| 2008-12-25T00:00:00    |
+------------------------+

https://cloud.google.com/bigquery/docs/reference/standard-sql/datetime_functions?hl=ja#datetime_trunc