SQLite offers several features not found in many other database systems. The most notable difference is that SQLite uses a dynamic-type system for tables. The SQLite engine will allow you to put any value into nearly any column, regardless of type. This is a major departure from traditional database systems, which tend to be statically typed. In many ways, the dynamic-type system in SQLite is similar to those found in popular scripting languages, which often have a single scalar type that can accept anything from integers to strings. In my own experience, the dynamic-type system has solved many more problems than it has caused.
Another useful feature is the ability to manipulate more than one database at a time. SQLite allows a single database connection to associate itself with multiple database files simultaneously. This allows SQLite to process SQL statements that bridge across multiple databases. This makes it trivial to join tables from different databases with a single query, or bulk copy data with a single command.
SQLite also has the ability to create fully in-memory databases. These are essentially database “files” that have no backing store and spend their entire lifetime within the file cache. While in-memory databases lack durability and do not provide full transaction support, they are very fast (assuming you have enough RAM), and are a great place to store temporary tables and other transient data.
There are a number of other features that make SQLite extremely flexible. Many of these, like virtual tables, are based off similar features found in other products, but with their own unique twist. These features and extensions provide a number of powerful tools to adapt SQLite to your own particular problem or situation.
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