BigQuery Standard SQL - Join on date with different formats

Question

I'd like to perform a join between two tables using the date column. However, since they come from two different dataset, the tables use two different formats:

Table_1 -> date: 2020-04-23 17:00:00 UTC
Table 2 -> date: 2020-04-11

Is there a way to do this in BigQuery in standard SQL?

Answer 1

Date columns do not have different formats. date is a built-in data type. But there are three types for storing date/times: date , datetime , and timestamp .

You can convert datetime and timestamp s to dates. That allows you to do:

from table_1 t1 join
     table_2 t2
     on date(t2.timestamp) = t1.date

You may want to include a timezone specified in the logic as well, but your question does not reference this. It assumes the days are UTC as well.