Database manipulation

We can manipulate data through database paths. The following piece of code declares a testdb database and defines several paths:

type Student = {int id, string name, int age}
database testdb {
    int               /basic/i     //Basic type int
    float             /basic/f     //Basic type float
    string            /basic/s     //Basic type string
    Student           /stu         //Record
    list(string)      /lst         //List
    intmap(Student)   /stumap      //Map
    Student           /stuset[{id}]     //Set
}

Type student that we defined ourselves. In addition to this type, our example covers the datatypes that are most frequently used in databases.

Each database path has a default value. Whenever we attempt to read a value that does not exist (either because it was never initialized or it has been removed), the default value is returned. The following list shows the default values for different types:

• The default value for an integer (int) is 0

• The default...