tl;dr: Instead of JOIN .. USING()
always prefer JOIN .. ON
.
You are right to be suspicious of the results. Given your staging, only one of these queries returns without errors:
select a.date_1, id_1
from AE_USING_TST_A a
left join AE_USING_TST_B b
on a.date_1 = b.date_2
join AE_USING_TST_C v
using(id_1)
where A.date_1 >= date('2020-10-01')
-- Can not convert parameter 'DATE('2020-10-01')' of type
-- [DATE] into expected type [NUMBER(38,0)]
;
select a.date_1, a.id_1
from AE_USING_TST_A a
left join AE_USING_TST_B b
on a.date_1 = b.date_2
join AE_USING_TST_C v
on a.id_1=v.id_1
where A.date_1 >= date('2020-10-01')
-- 2020-10-11 2
;
I would call this a bug, except that the documentation is clear about not doing this kind of queries with JOIN .. USING
:
To use the USING clause properly, the projection list (the list of columns and other expressions after the SELECT keyword) should be “*”. This allows the server to return the key_column exactly once, which is the standard way to use the USING clause. For examples of standard and non-standard usage, see the examples below.
https://docs.snowflake.com/en/sql-reference/constructs/join.html
The documentation doubles down on the problems of using USING()
on non-standard situations, with a different query acting "wrong":
The following example shows non-standard usage; the projection list contains something other than “*”. Because the usage is non-standard, the output contains two columns named “userid”, and the second occurrence (which you might expect to contain a value from table ‘r’) contains a value that is not in the table (the value ‘a’ is not in the table ‘r’).
So just prefer JOIN .. ON
. For extra discussion on the SQL ANSI standard not defining behavior for some cases of USING()
check: