joins in coredata using Objective C

问题

How to make inner joins,outer joins(left,right,full) in core-data. I have done it easily in sqlite db using sqlite c based APIs But I couldn't find any resources on how to do it using core-data in Objective C.

Basically I have a need to query CoreData that involves relation between more than three tables or objects.

Note:

How to set relationship between tables in core-data would be helpful. such as Primary key - foreign key relationship,cascade relationship.

回答1:

To query Core Data you need to create NSPredicates for that and its clearly stated in documentation that you cannot convert any arbitrary query into NSPredicates.

For more info read this :-https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/Predicates/Articles/pUsing.html

来源：https://stackoverflow.com/questions/32932521/joins-in-coredata-using-objective-c