When to Use SQLite instead of Core Data on the iPhone

This excerpt from Using SQLite explains the differences between Core Data and SQLite and will help you decide which to use when developing on the iPhone.

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When the iPhone and iPod touch were first released, Apple heavily advocated the use of SQLite. The SQLite library was provided as a system framework and was well documented, complete with code examples, in the SDK.

With the release of version 3.0, Apple has made their Core Data system available on the iPhone OS. Core Data has been available on the Macintosh platform for a number of years, and provides a high-level data abstraction framework that offers integrated design tools and runtime support to address complex data management needs. Unlike SQLite, the Core Data model is not strictly relational in nature.

Now that the higher level library is available on their mobile platform, Apple is encouraging people to migrate to Core Data. Most of the SQLite documentation and code examples have been removed from the SDK, and the system-level framework is no longer available. However, because Core Data utilizes SQLite in its storage layer, there is still a standard SQLite system library available for use. It is also relatively easy to compile application-specific versions of the SQLite library. This is required if you want to take advantage of some of the more recent features, as the system version of SQLite is often several versions behind.

Core Data has some significant advantages. Apple provides development tools that allow a developer to quickly lay out their data requirements and relationships. This can reduce development time and save on code. The Core Data package is also well integrated into current Mac OS X systems, allowing data to move back and forth between the platforms quite easily.

For all the advantages that Core Data provides, there are still situations where it makes sense to use SQLite directly. The most obvious consideration is if your development needs extend beyond Apple platforms. Unlike Core Data, the SQLite library is available on nearly any platform, allowing data files to be moved and accessed almost anywhere on any platform. Core Data also uses a different storage and retrieval model than SQLite. If your application is particularly well suited to the Relational Model, there may be advantages to having direct SQL query access to the data storage layer. Using the SQLite library directly also eliminates a number of abstraction layers from the application design. While this may lead to more detailed code, it is also likely to result in better performance, especially with larger datasets.

Like many engineering choices, there are benefits and concerns with both approaches. Assuming the platform limitations aren’t a concern, Core Data can provide a very rapid solution for moderately simple systems. On the other hand, SQLite allows better cross-platform compatibility (in both code and data), and allows direct manipulation of complex data models. If you’re not dependent on the latest version of SQLite, you may even be able to reduce the size of your application by using the existing SQLite system library. Which set of factors has higher value to you is likely to be dependent on your platform requirements, and the complexity of your data model.