Why my SOQL return error

Question

SOQL

SELECT Name, AirRegulator__c, AmountReview__c, BatteryCapacity__c, 
       ChargingTime__c, Length__c, NumberUnits__c, Rating__c, TankSize__c, 
       (SELECT UnitPrice FROM PricebookEntries) 
FROM Product2 
WHERE Id IN (SELECT Product2Id FROM PricebookEntries WHERE UnitPrice = 1)
LIMIT 4

Error

sObject type 'PricebookEntries' is not supported. If you are attempting to use a custom object, be sure to append the '__c' after the entity name. Please reference your WSDL or the describe call for the appropriate names.

PricebookEntries is not custom object

Answer 1

Your sub-select is the problem.

(SELECT Product2Id FROM PricebookEntries WHERE UnitPrice = 1)

PricebookEntries is a relationship name, not an sObject name. The sObject name, which you must use in a top-level SOQL query (as opposed to the parent-child subquery you're also using) is PricebookEntry.

Note that this exposes a subtle difference between your parent-child subquery and your sub-select. Each Product2 row in your query results will include a PricebookEntries relationship that contains all PricebookEntries for that product.

However, you'll only get back Product2 records that have at least one PricebookEntry whose UnitPrice is 1.