# USQL - User sessions query  - Filter based on computed value

**URL:** <https://community.dynatrace.com/t/usql-user-sessions-query-filter-based-on-computed-value/55860>\
**Category:** Real User Monitoring\
**Tags:** usql\
**Created:** [May 11, 2026, 1:22am UTC](https://community.dynatrace.com/t/usql-user-sessions-query-filter-based-on-computed-value/55860 "2026-05-11T01:22:54Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![kmahali](https://avatars.discourse-cdn.com/v4/letter/k/e274bd/32.png) [@kmahali](https://community.dynatrace.com/u/kmahali)\
**Post date:** [May 11, 2026, 1:22am UTC](https://community.dynatrace.com/t/usql-user-sessions-query-filter-based-on-computed-value/55860/1 "2026-05-11T01:22:54Z")

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```python
SELECT
  usersession.startTime,
  userevent.startTime ,
  usersession.userSessionId,
  usersession.stringProperties.user_loginid,
  (userevent.startTime - usersession.startTime )/60000 AS error_occurrence
FROM userevent
WHERE page = '/error_page'
AND error_occurrence > 5

```

The above query would not work; it shows error ‘Unknown field:&nbsp;error\_occurrence’. Is there any other option to achieve this?

---

<div class="post-metadata">

**Author:** ![Khejazi](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/khejazi/32/9921_2.png) [@Khejazi](https://community.dynatrace.com/u/Khejazi)\
**Post date:** [May 11, 2026, 8:30am UTC](https://community.dynatrace.com/t/usql-user-sessions-query-filter-based-on-computed-value/55860/2 "2026-05-11T08:30:51Z")

</div>

Hi,

Unfortunately, you can’t use Alias in Where clause, you can use only fields.

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<div class="post-metadata">

**Author:** ![kmahali](https://avatars.discourse-cdn.com/v4/letter/k/e274bd/32.png) [@kmahali](https://community.dynatrace.com/u/kmahali)\
**Post date:** [May 11, 2026, 11:26am UTC](https://community.dynatrace.com/t/usql-user-sessions-query-filter-based-on-computed-value/55860/3 "2026-05-11T11:26:48Z")

</div>

Thanks Khejazi, for your reply.

`AND (userevent.startTime - usersession.startTime )/60000 \> 5`  
Even with the fields arithmetic is not allowed. Is there any workaround for this?

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<div class="post-metadata">

**Author:** ![Khejazi](https://dub1.discourse-cdn.com/dynatrace/user_avatar/community.dynatrace.com/khejazi/32/9921_2.png) [@Khejazi](https://community.dynatrace.com/u/Khejazi)\
**Post date:** [May 11, 2026, 11:55am UTC](https://community.dynatrace.com/t/usql-user-sessions-query-filter-based-on-computed-value/55860/4 "2026-05-11T11:55:07Z")

</div>

It will be the same since you are using an expression which is not originally a field in the table