Are these two Spark SQL queries the same in terms of logic? - sql

Question

I have two queries that I think should be doing the same thing logically, but in reality return different results. The goal is to find rows parsed out of HTTP requests that have a controller_type like one of a few conditions, and where the controller_context_id is not NULL or ''. If these conditions are met, give the row a value of one, sum all those up, and group them together. This first query was incorrectly including rows with a controller_context_id that weren't populated:
SELECT
TRUNC(request_timestamp, 'month') AS request_timestamp,
account_id,
account_guid,
cluster_id,
shard_id,
unique_id,
context_id,
controller_type,
controller_context_id,
concat_user_id,
user_id,
COUNT(account_id) AS num_page_views,
SUM(CASE
WHEN controller_type LIKE 'pages%' AND
controller_context_id <> '' AND
controller_context_id IS NOT NULL
THEN 1
ELSE 0 END) AS num_page_views_pages,
SUM(CASE
WHEN controller_type LIKE 'files%' AND
controller_context_id <> '' AND
controller_context_id IS NOT NULL
THEN 1
ELSE 0 END) AS num_page_views_files,
SUM(CASE
WHEN controller_type LIKE 'modules%' AND
controller_context_id <> '' AND
controller_context_id IS NOT NULL
THEN 1
ELSE 0 END) AS num_page_views_modules,
SUM(CASE
WHEN controller_type LIKE 'assignments%' AND
controller_context_id <> '' AND
controller_context_id IS NOT NULL
THEN 1
ELSE 0 END) AS num_page_views_assignments,
SUM(CASE
WHEN controller_type LIKE 'quizzes%' AND
controller_context_id <> '' AND
controller_context_id IS NOT NULL
THEN 1
ELSE 0 END) AS num_page_views_quizzes,
SUM(CASE
WHEN controller_type LIKE 'discussion_topics%' AND
controller_context_id <> '' AND
controller_context_id IS NOT NULL
THEN 1
ELSE 0 END) AS num_page_views_discussion_topics,
SUM(CASE
WHEN controller_type LIKE 'outcome%' AND
controller_context_id <> '' AND
controller_context_id IS NOT NULL
THEN 1
ELSE 0 END) AS num_page_views_outcomes,
COUNT(DISTINCT session_id) AS num_sessions
FROM requests
GROUP BY
TRUNC(request_timestamp, 'month'),
account_id,
account_guid,
cluster_id,
shard_id,
unique_id,
context_id,
context_id,
controller_type,
controller_context_id,
concat_user_id,
user_id
Where this second query does the correct thing:
SELECT
TRUNC(request_timestamp, 'month') AS request_timestamp,
account_id,
account_guid,
cluster_id,
shard_id,
unique_id,
context_id,
controller_type,
controller_context_id,
concat_user_id,
user_id,
COUNT(account_id) AS num_page_views,
COUNT(DISTINCT session_id) AS num_sessions,
SUM(CASE
WHEN controller_type LIKE 'pages%' AND
(CASE
WHEN controller_context_id = '' OR
controller_context_id IS NULL THEN 0 ELSE 1 END)
= 1
THEN 1
ELSE 0 END) AS num_page_views_pages,
SUM(CASE
WHEN controller_type LIKE 'files%' AND
(CASE
WHEN controller_context_id = '' OR
controller_context_id IS NULL THEN 0 ELSE 1 END)
= 1
THEN 1
ELSE 0 END) AS num_page_views_files,
SUM(CASE
WHEN controller_type LIKE 'modules%' AND
(CASE
WHEN controller_context_id = '' OR
controller_context_id IS NULL THEN 0 ELSE 1 END)
= 1
THEN 1
ELSE 0 END) AS num_page_views_modules,
SUM(CASE
WHEN controller_type LIKE 'assignments%' AND
(CASE
WHEN controller_context_id = '' OR
controller_context_id IS NULL THEN 0 ELSE 1 END)
= 1
THEN 1
ELSE 0 END) AS num_page_views_assignments,
SUM(CASE
WHEN controller_type LIKE 'quizzes%' AND
(CASE
WHEN controller_context_id = '' OR
controller_context_id IS NULL THEN 0 ELSE 1 END)
= 1
THEN 1
ELSE 0 END) AS num_page_views_quizzes,
SUM(CASE
WHEN controller_type LIKE 'discussion_topics%' AND
(CASE
WHEN controller_context_id = '' OR
controller_context_id IS NULL THEN 0 ELSE 1 END)
= 1
THEN 1
ELSE 0 END) AS num_page_views_discussion_topics,
SUM(CASE
WHEN controller_type LIKE 'outcomes%' AND
(CASE
WHEN controller_context_id = '' OR
controller_context_id IS NULL THEN 0 ELSE 1 END)
= 1
THEN 1
ELSE 0 END) AS num_page_views_outcomes
FROM requests
GROUP BY
TRUNC(request_timestamp, 'month'),
account_id,
account_guid,
cluster_id,
shard_id,
unique_id,
context_id,
controller_type,
controller_context_id,
concat_user_id,
user_id
As far as I can tell they should be doing the same thing, the second query just uses a nested CASE statement to check for the NULL or '' value. I'm having trouble understanding the difference, if any, in logic between the two.