Sql query to find count with a difference condition and total count in the same query - sql

Question

Here is a sample table I have
Logs
user_id, session_id, search_query, action
1, 100, dog, A
1, 100, dog, B
2, 101, cat, A
3, 102, ball, A
3, 102, ball, B
3, 102, kite, A
4, 103, ball, A
5, 104, cat, A
where
miss = for the same user_id and same session id , if action A is not followed by action B its termed a miss.
Note: action B can happen only after action A has happened.
I am able to find the count of misses for each unique search_query across all users and sessions.
SELECT l1.search_query, count(l1.*) as misses
FROM logs l1
WHERE NOT EXISTS
(SELECT NULL FROM logs l2
WHERE l1.user_id = l2.user_id
AND l1.session_id = l2.session_id
AND l1.session_id != ''
AND l2.action = 'B'
AND l1.action = 'A')
AND l1.action='A'
AND l1.search_query != ''
GROUP BY v1.search_query
order by misses desc;
I am trying to find the value of miss_percentage=(number of misses/total number of rows)*100 for each unique search_query. I couldn't figure out how to find the count with a condition and count without that condition in the same query. Any help would be great.
expected output:
cat 100
kite 100
ball 50

Answer 1

One way to do it is to move the EXISTS into the count
SELECT l1.search_query, count(case when NOT EXISTS
(SELECT 1 FROM logs l2
WHERE l1.user_id = l2.user_id
AND l1.session_id = l2.session_id
AND l1.search_query = l2.search_query
AND l2.action = 'B'
AND l1.action = 'A') then 1 else null end
)*100.0/count(*) as misses
FROM logs l1
WHERE l1.action='A'
AND l1.search_query != ''
GROUP BY l1.search_query
order by misses desc;
This produces the desired results, but also zeros if no misses were found. This can be removed with a HAVING clause, or postprocessing.
Note I also added the clause l1.search_query = l2.search_query that was missing, since otherwise it was counting kite as succeeded, since there is a row with B in the same session.

Answer 2

I think you just need to use case statements here. If I have understood your problem correctly .. then the solution would be something like this -
WITH summary
AS (
SELECT user_id
,session_id
,search_query
,count(1) AS total_views
,sum(CASE
WHEN action = 'A'
THEN 1
ELSE 0
END) AS action_a
,sum(CASE
WHEN action = 'B'
THEN 1
ELSE 0
END) AS action_b
FROM logs l
GROUP BY user_id
,session_id
,search_query
)
SELECT search_query
,(sum(action_a - action_b) / sum(action_a)) * 100 AS miss_percentage
FROM summary
GROUP BY search_query;

Answer 3

You can allways create two queries, and combine them into one with a join. Then you can do the calculations in the bridging (or joining) SQL statement.
In MS-SQL compatible SQL this would be:
SELECT ActiontypeA,countedA,isNull(countedB,0) as countedB,
(countedA-isNull(countedB,0))*100/CountedA as missed
FROM (SELECT search_query as actionTypeA, count(*) as countedA
FROM logs WHERE Action='A' GROUP BY actionType
) as TpA
LEFT JOIN
(SELECT search_query as actionTypeB, count(*) as countedB
FROM logs WHERE Action='B' GROUP BY actionType
) as TpB
ON TpA.ActionTypeA = TpB.ActiontypeB
The LEFT JOIN is required to select all activities (search_query) from the 'A' results, and join them to only those from the 'B' results where a B is available.
Since this is very basic SQL (and well optimized by SQL engines) I'd suggest to prevent WHERE EXISTS as much as possible. The IsNull() function is an MS-SQL function to force a NULL value into the int(0) value which can be used in a calculation.
Finally you could filter on
WHERE missed>0
to get the final result.