How will SQL Server execute this WITH clause - sql-server

Question

I have the following query. Here 'B' is giving me non repeated MessageIds and i am using them in subquery with A, B is internally using A.
So when i call SELECT in the last part, will it execute A again or will it use data already fetched while B was being called ?
WITH A as (
SELECT z.Name, ze.Inside, ze.MessageId, ze.DateTime
FROM ZoneStateEntries ze
INNER JOIN Zone z
ON ze.ZoneId = z.ZoneId
WHERE ze.ObjectId = 1324
AND (Inside = 1 OR Inside = 0)
AND ze.DateTime BETWEEN '2018-10-22 00:00:00' AND '2019-11-05 00:00:00'
),
B as (
SELECT a.MessageId
FROM A a
INNER JOIN A b
on a.MessageId = b.MessageId
GROUP BY a.MessageId
HAVING COUNT(a.MessageId) = 1
)
SELECT *
FROM A
WHERE MessageId IN (
SELECT *
FROM B
)
AND a.Inside = 1
ORDER BY DateTime DESC
The data here is huge and we can't afford to execute query A multiple times. Can we optimize it further?

Answer 1

A a INNER JOIN A b looks like unnecessary. You can use COUNT(DISTINCT MessageId) for getting unique messages.
WITH A as (
SELECT z.Name, ze.Inside, ze.MessageId, ze.DateTime
FROM ZoneStateEntries ze
INNER JOIN Zone z
ON ze.ZoneId = z.ZoneId
WHERE ze.ObjectId = 1324
AND (Inside = 1 OR Inside = 0)
AND ze.DateTime BETWEEN '2018-10-22 00:00:00' AND '2019-11-05 00:00:00'
)
SELECT *
FROM A
WHERE MessageId IN (
SELECT MessageId
FROM A
GROUP BY MessageId
HAVING COUNT(DISTINCT MessageId) = 1
)
AND a.Inside = 1
ORDER BY DateTime DESC