Patience, Grasshopper. You posted on a Sunday when most users are living their lives rather than hanging out here. Even on work days, it may take a while to get an answer, especially when the question doesn't describe the desired result.
Have you tried using append to combine the two queries?
|dbxquery query="SELECT \"id\", \"name\", \"chain\" FROM flows;" connection="Postgres"
| append [ search index=xyz sourcetype=xy source="logs" groups (CLIENT_Id ="*") |rex field=Request_URL "\/(?<Group>[^\/]+)$"
| convert timeformat="%Y-%m-%d" ctime(_time) AS Date
| stats count by Date CLIENT_Id GroupRequest_URL
| sort - CLIENT_Id
| rename Group as id ]
| stats values(*) as * by id
--- If this reply helps you, an upvote would be appreciated.