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Editorial Team
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Asked: 2026-06-09T10:13:19+00:00

I have imported a mysql from a web app into my iOS app. This

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I have imported a mysql from a web app into my iOS app. This database is designed specifically without using foreign keys.

I need to do a Left-Join but I can’t figure out how to do this in iOS core-data without using a relationship.

Is there not a way to just get two tables data using a Data.id == Item.id like syntax in a
NSPredicate???

———-EDITED———-

To put it more specifically I want to take a Data entity with and match the item attribute with the Entity Item’S entity code attribute. Any “objects” that don’t have a match should not be included.

Just like a left join….. Ya feel me?

I am stumped.

Help
Thanks.

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1 Answer

  1. Editorial Team

    You ask “is there no easy way in core data“?
    Turns out, it is much easier in core data than in SQL.

    Simply make entity Item a relationship of entity Data. Your predicate could then be 

    [NSPredicate predicateWithFormat:@"item = %@", itemObject];

    What could be easier than that??

    Assumptions: relationship is one-to-one, name of relationship is item, itemObject is a managed object of type Item.

    For the record: you are actually not even dealing with a table, because Core Data is an object graph and not a database. You will find many discussions on this here on SOF.

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