Select

The select clause in FQL does what you expect it to do. It is a projection from the original structure to the defined field list in the clause.

Field list

In the select statement you define a field list. Fields are separated by a comma. And a field can have several forms:

Simple field name

You can just define a field name just like you would do in SQL.

    from Patient 
    select
        name

Of course this does not produce a single value. The field 'name' is actually a FhirPath expression. That means that if there is more than one name in the resource, they will all go to the output.

Name is also a tree in itself, because it contains sub fields. This query will therefore also produce a set of name-trees in the output.

All fields

You can use the * field to select all fields in a select statement:

from Patient
select *

FhirPath field

As long as you describe an actual path, you can use FhirPath as a field designator: The following syntaxes are valid:

from Patient
select
    meta.profile,
    name[0].family
    name.given,
    name.given[0]
    

Note that a FhirPath statement can have more than one result. Since name.given can have multiple values, your select set will result in an array for the field given as well. It will not give you the name structure.

JSON like field definitions

You can expclitly set the name of a field by using JSON format:

...
select
    lastname: name[0].family,
    firstname: name[0].given

This allows you to set the name of a field. But it also allows defining full fhirpath expressions:

...
select
    firstname: name.given.first()