Querying

The feed supports these OData system query options. Anything else — $expand, $search, $apply — answers 501 Not Implemented rather than being silently ignored, so a response always means exactly what you asked for.

Option	What it does	Example
`$filter`	Keep only the rows matching an expression	`$filter=visitDate ge 2026-01-01`
`$orderby`	Sort by one or more properties, `asc` (default) or `desc`; empty values come first ascending and last descending, as OData specifies	`$orderby=visitDate desc`
`$top`	Page size, at most 1000 (also the default)	`$top=500`
`$skip`	Rows to skip before the page	`$skip=1000`
`$count`	`true` adds `@odata.count`, the total matching rows	`$count=true`
`$select`	Return only these properties (the key is always kept)	`$select=id,visitDate,quantityTotal`

Each set also answers GET /<Set>/$count with the plain number of rows, $filter applied.

Filter expressions

Comparisons eq ne gt ge lt le, combined with and, or, not and parentheses, plus the text functions contains, startswith and endswith (these match case-insensitively).

Literals: 'strings' (double a quote to escape it: 'It''s'), numbers, true/false, null (with eq/ne only), GUIDs quoted or bare, dates (2026-01-01) and timestamps (2026-01-01T10:00:00Z, any offset).


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$filter=visitDate ge 2026-01-01 and visitDate lt 2026-02-01
$filter=quantityTotal gt 2 or origin eq null
$filter=contains(email, '@example.dk') and archived eq false
$filter=type eq 'ORDER' and amount ge 100
$filter=ticketTypeId eq bd4a0997-39db-41d9-883a-cdfa83e2101f

A filter on a property the set does not have, a type mismatch (quantityTotal eq 'two'), or anything the grammar cannot read is a 400 with an error code — never a silently dropped condition.

Paging

Large results come in pages. When a page is full, the response carries @odata.nextLink: the same query with $skip advanced and every option — filter, order, selection, count — kept. Follow it until it disappears. OData clients (Power BI, Excel) do this on their own; rows are ordered stably, so pages never overlap.

Errors

Errors are OData JSON with a code:


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{ "error": { "code": "UNKNOWN_FILTER_FIELD", "message": "Unknown property visitdate in $filter." } }

401 means no key reached the feed, 403 an invalid key or one without OData access, 400 a request the feed cannot read, 404 an unknown set or entity, 501 an OData option the feed does not implement.