He left out an important reason to know and use SQL directly: you should always be aware how you are using your indices. This goes beyond making an index for a

He left out an important reason to know and use SQL directly: you should always be aware how you are using your indices. This goes beyond making an index for a column in the table: you also need to know whether the query will map well to a btree index. Mobile, with its low resources, makes index optimization even more important; apple's Core Data can easily kill your app.