Joining tables on dataverse outside dynamic 365 CRM, you can use power query

You can use fetch xml/Query expressions to join the tables inside crm

or

Open excel sheet and save it

Goto dataà select get data in advance copy paste the API URL

signing with the organization account

then connect

you will find tables and select tables you want

click on combine select the columns from the tables using below dropdown

and select the joins as asked please and

click on the double arrows to get the columns of the other table

and click close and load the data