4. Data access and transformation

DataQL reads data through paths and shapes results with =>. External parameters, current transformation items and local variables have distinct access forms.

• Fields and indexes: object fields, list indexes, missing values and bounds.
• Parameters and context: parameter scopes such as ${name}, and $, @, # in transformations.
• Result transformation: select, rename, calculate and nest fields.

var order = {"id": 10, "customer": {"name": "Alice"}, "items": [{"price": 20, "count": 3}]};
return order => {
    "id",
    "customerName": customer.name,
    "lines": items => [{"amount": price * count}]
};

{"id":10,"customerName":"Alice","lines":[{"amount":60}]}

Object templates select fields; list templates transform items. Use collection functions for filtering, sorting and grouping.