I am trying to write an inner join and noticed from some other threads you need to write it similar to this 

services/data/v47.0/query/?q=SELECT+Id,Name,(select+OpportunityId,Price+From+OpportunityLineItem) +From+Opportunity+Where+Opportunity.Id+=+OpportunityLineItem.OpportunityId

this returns a MALFORMED_QUERY errorCode. Is this query possible if so what would be the correct way to write this. 

Thanks in advance