Filter Documentation¶

The Danish Parliament API's $filter parameter provides powerful querying capabilities with full support for text search, date operations, and complex logical expressions. This guide covers all filtering syntax with practical Danish parliamentary data examples.

Filter Syntax Overview¶

The API uses OData 3.0 filter syntax with these key operators and functions:

Comparison Operators¶

Operator	Meaning	Example
`eq`	Equals	`offentlighedskode eq 'O'`
`ne`	Not equals	`offentlighedskode ne 'O'`
`gt`	Greater than	`id gt 100000`
`ge`	Greater or equal	`id ge 100000`
`lt`	Less than	`year(opdateringsdato) lt 2025`
`le`	Less or equal	`year(opdateringsdato) le 2024`

Logical Operators¶

Operator	Meaning	Example
`and`	Logical AND	`offentlighedskode eq 'O' and year(opdateringsdato) eq 2025`
`or`	Logical OR	`substringof('klima',titel) or substringof('miljø',titel)`
`not`	Logical NOT	`not (offentlighedskode eq 'O')`

String Functions (Danish Text Search)¶

substringof() - Text Contains¶

Most commonly used function for searching Danish parliamentary content:

# Find climate legislation (klima = climate)
curl "https://oda.ft.dk/api/Sag?%24filter=substringof('klima',titel)&%24top=5"

# Find environment-related cases (miljø = environment)
curl "https://oda.ft.dk/api/Sag?%24filter=substringof('miljø',titel)&%24top=5"

# Search for minister mentions (ministeren = the minister)
curl "https://oda.ft.dk/api/Sag?%24filter=substringof('ministeren',titel)&%24top=5"

# Find EU-related legislation
curl "https://oda.ft.dk/api/Sag?%24filter=substringof('eu',titel)&%24top=5"

startswith() - Text Prefix¶

Perfect for finding specific types of parliamentary documents:

# Find legislative proposals (Forslag = Proposal)
curl "https://oda.ft.dk/api/Sag?%24filter=startswith(titel,'Forslag')&%24top=5"

# Find committee reports (Betænkning = Report)
curl "https://oda.ft.dk/api/Sag?%24filter=startswith(titel,'Betænkning')&%24top=5"

# Find government bills (Lovforslag = Bill)
curl "https://oda.ft.dk/api/Sag?%24filter=startswith(titel,'Lovforslag')&%24top=5"

endswith() - Text Suffix¶

Useful for finding documents by their conclusion type:

# Find laws (ends with 'lov')
curl "https://oda.ft.dk/api/Sag?%24filter📁ndswith(titel,'lov')&%24top=5"

# Find questions (ends with '?')
curl "https://oda.ft.dk/api/Sag?%24filter📁ndswith(titel,'%3F')&%24top=5"

Date and Time Functions¶

year() - Extract Year¶

# All cases from 2025
curl "https://oda.ft.dk/api/Sag?%24filter=year(opdateringsdato)%20eq%202025&%24top=10"

# Historical cases from specific years
curl "https://oda.ft.dk/api/Sag?%24filter=year(opdateringsdato)%20eq%201995&%24top=5"

# Cases from multiple years
curl "https://oda.ft.dk/api/Sag?%24filter=(year(opdateringsdato)%20eq%202024%20or%20year(opdateringsdato)%20eq%202025)&%24top=10"

month() and day() - Specific Dates¶

# Cases updated in September (month 9)
curl "https://oda.ft.dk/api/Sag?%24filter=month(opdateringsdato)%20eq%209&%24top=10"

# Cases from a specific day
curl "https://oda.ft.dk/api/Sag?%24filter=day(opdateringsdato)%20eq%209%20and%20month(opdateringsdato)%20eq%209&%24top=5"

DateTime Comparisons¶

# Cases updated since January 1st, 2025
curl "https://oda.ft.dk/api/Sag?%24filter=opdateringsdato%20gt%20datetime'2025-01-01T00:00:00'&%24top=10"

# Cases updated today (replace with current date)
curl "https://oda.ft.dk/api/Sag?%24filter=opdateringsdato%20gt%20datetime'2025-09-09T00:00:00'&%24top=10"

# Date range queries
curl "https://oda.ft.dk/api/Sag?%24filter=opdateringsdato%20gt%20datetime'2025-09-08T00:00:00'%20and%20opdateringsdato%20lt%20datetime'2025-09-09T00:00:00'&%24top=5"

Complex Filter Examples with Danish Content¶

Legislative Type Filtering¶

# Climate AND environment legislation
curl "https://oda.ft.dk/api/Sag?%24filter=(substringof('klima',titel)%20or%20substringof('miljø',titel))%20and%20year(opdateringsdato)%20gt%202020&%24top=5"

# Government proposals vs. member proposals
curl "https://oda.ft.dk/api/Sag?%24filter=startswith(titel,'Forslag')%20and%20substringof('regeringen',titel)&%24top=5"

# Budget-related legislation (budget = budget)
curl "https://oda.ft.dk/api/Sag?%24filter=(substringof('budget',titel)%20or%20substringof('finanslov',titel))&%24top=5"

Actor-Based Filtering¶

# Cases involving specific politicians
curl "https://oda.ft.dk/api/Stemme?%24filter=Aktør/navn%20eq%20'Frank%20Aaen'&%24expand=Afstemning&%24top=10"

# Cases from specific committees
curl "https://oda.ft.dk/api/SagAktør?%24filter=substringof('udvalg',Aktør/navn)&%24expand=Sag,Aktør&%24top=10"

Status and Category Filtering¶

# Only public cases
curl "https://oda.ft.dk/api/Sag?%24filter=offentlighedskode%20eq%20'O'&%24top=10"

# Cases by specific status
curl "https://oda.ft.dk/api/Sag?%24filter=Sagsstatus/status%20eq%20'Afsluttet'&%24expand=Sagsstatus&%24top=5"

Danish Character Support¶

The API fully supports Danish special characters in filters:

Vowels with Accents¶

# Search for ø character
curl "https://oda.ft.dk/api/Aktør?%24filter=substringof('ø',navn)&%24top=3"

# Search for å character  
curl "https://oda.ft.dk/api/Aktør?%24filter=substringof('å',navn)&%24top=3"

# Search for æ character
curl "https://oda.ft.dk/api/Aktør?%24filter=substringof('æ',navn)&%24top=3"

Common Danish Terms in Politics¶

# Folketinget (Parliament)
curl "https://oda.ft.dk/api/Sag?%24filter=substringof('Folketinget',titel)&%24top=5"

# Statsministeren (Prime Minister)
curl "https://oda.ft.dk/api/Sag?%24filter=substringof('statsministeren',titel)&%24top=5"

# Finansministeren (Finance Minister)
curl "https://oda.ft.dk/api/Sag?%24filter=substringof('finansministeren',titel)&%24top=5"

# Udvalg (Committee)
curl "https://oda.ft.dk/api/Aktør?%24filter=substringof('udvalg',navn)&%24top=5"

Critical Filter Warnings¶

Silent Filter Failures

Invalid filter field names are silently ignored and return the complete unfiltered dataset. This is the most dangerous behavior in the API.

# This returns ALL records (not an error!)
curl "https://oda.ft.dk/api/Sag?%24filter=invalid_field%20eq%20'test'&%24top=5"  # Returns 100 records!

How to Detect Silent Failures¶

Always test with small $top values first:

# Test your filter with a small result set
curl "https://oda.ft.dk/api/Sag?%24filter=your_filter_here&%24top=1"

Monitor result counts:

# Python: Check for unexpected result sizes
response = requests.get(url)
data = response.json()
if len(data['value']) == 100 and '$top=100' not in url:
    print("Warning: Filter may have been ignored")

Validate field names against OData metadata:

# Get valid field names for an entity
curl "https://oda.ft.dk/api/\$metadata" | grep "Property Name"

URL Encoding Requirements¶

Critical: Special Character Encoding

All special characters in filters must be URL encoded:

Character	Encoding	Example
`$`	`%24`	`%24filter=`
Space	`%20`	`navn%20eq%20'Frank%20Aaen'`
`'`	`%27`	`eq%20%27O%27`
`(`	`%28`	`%28substringof`
`)`	`%29`	`titel%29`
`?`	`%3F`	`endswith(titel,'%3F')`

Performance Optimization¶

Filter Early, Expand Late¶

# Efficient: Filter first, then expand
curl "https://oda.ft.dk/api/Sag?%24filter=year(opdateringsdato)%20eq%202025&%24expand=Sagskategori&%24top=10"

# Less efficient: Expand everything, then filter  
curl "https://oda.ft.dk/api/Sag?%24expand=Sagskategori,Sagstrin,SagAktør&%24filter=year(opdateringsdato)%20eq%202025&%24top=10"

Index-Friendly Filters¶

The API performs best with these filter patterns: - ID-based filtering: id eq 12345 - Year-based filtering: year(opdateringsdato) eq 2025 - Exact string matches: offentlighedskode eq 'O'

Entity-Specific Filter Examples¶

Sag (Cases) Entity¶

# Public legislation from current year
curl "https://oda.ft.dk/api/Sag?%24filter=offentlighedskode%20eq%20'O'%20and%20year(opdateringsdato)%20eq%202025&%24top=10"

# Bills containing climate provisions
curl "https://oda.ft.dk/api/Sag?%24filter=substringof('lovforslag',titel)%20and%20substringof('klima',titel)&%24top=5"

Aktør (Actors) Entity¶

# Current members of parliament (active politicians)
curl "https://oda.ft.dk/api/Aktør?%24filter=Aktørtype/type%20eq%20'person'%20and%20substringof('MF',navn)&%24expand=Aktørtype&%24top=10"

# Parliamentary committees
curl "https://oda.ft.dk/api/Aktør?%24filter=substringof('udvalg',navn)&%24top=10"

Stemme (Votes) Entity¶

# Votes by specific politician on climate issues
curl "https://oda.ft.dk/api/Stemme?%24filter=Aktør/navn%20eq%20'Frank%20Aaen'&%24expand=Aktør,Afstemning&%24top=10"

# All "yes" votes (typeid = 1)  
curl "https://oda.ft.dk/api/Stemme?%24filter=typeid%20eq%201&%24expand=Stemmetype&%24top=10"

Advanced Filter Patterns¶

Multi-Language Search¶

# Search in both Danish and English terms
curl "https://oda.ft.dk/api/Sag?%24filter=(substringof('klima',titel)%20or%20substringof('climate',titel))&%24top=5"

Temporal Filtering¶

# Recent activity (last 7 days)
curl "https://oda.ft.dk/api/Sag?%24filter=opdateringsdato%20gt%20datetime'2025-09-02T00:00:00'&%24top=10"

# Historical comparison (same month, different years)
curl "https://oda.ft.dk/api/Sag?%24filter=month(opdateringsdato)%20eq%209%20and%20(year(opdateringsdato)%20eq%202024%20or%20year(opdateringsdato)%20eq%202025)&%24top=10"

Negation Patterns¶

# Non-public cases
curl "https://oda.ft.dk/api/Sag?%24filter=not%20(offentlighedskode%20eq%20'O')&%24top=10"

# Cases NOT containing specific terms
curl "https://oda.ft.dk/api/Sag?%24filter=not%20substringof('eu',titel)&%24top=10"

Filter Function Reference¶

Tested and Working Functions¶

Function	Syntax	Purpose	Example
`substringof(needle, haystack)`	Text contains	`substringof('klima', titel)`	✅
`startswith(text, prefix)`	Text starts with	`startswith(titel, 'Forslag')`	✅
`endswith(text, suffix)`	Text ends with	`endswith(titel, 'lov')`	✅
`year(date)`	Extract year	`year(opdateringsdato) eq 2025`	✅
`month(date)`	Extract month	`month(opdateringsdato) eq 9`	✅
`day(date)`	Extract day	`day(opdateringsdato) eq 9`	✅

Unsupported Functions (OData 4.0+)¶

contains() - Use substringof() instead
toupper(), tolower() - Not available
length() - Not supported
indexof() - Not supported

Best Practices Summary¶

Always URL encode special characters ($ %24)
Test filters with small $top values first
Monitor result sizes to detect silent failures
Use specific field names from the metadata
Filter early before expanding relationships
Leverage Danish character support for authentic searches
Combine multiple criteria with logical operators
Validate field names against the OData metadata

The Danish Parliament API's filter capabilities provide exceptional access to 74+ years of parliamentary data when used correctly. Master these patterns and you'll efficiently find exactly the democratic information you need.