Query

• Formats
• Filter by Attributes
• Filter by Location
• Aggregation Statistics

Layers have a single endpoint for requesting features. The /query supports filtering by attributes, geography, time, as well as aggregate statistics.

Defaults

To request all the data, up to the maximum record count, you need to provide a few required parameters:

.../FeatureServer/0/query?where=1=1&outFields=*&f=json

This request states: “Return all the features all the attributes as JSON.”

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Formats

GeoServices support a few common formats. Most commonly these are html and json and depending on the version of Service can include geojson, kml, and amf. Format outputs are requested by using the URI parameter f={format}. html is the default response.

.../Education_WebMercator/MapServer/5?f=json

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Filter by Attributes

Examples

Total number of students by school type and number of zipcodes that have this school type:

http://maps2.dcgis.dc.gov/dcgis/rest/services/DCGIS_DATA/Education_WebMercator/MapServer/5/query
  ?where=FACUSE like 'Elementary School' AND ZIP_CODE=20002 AND STATUS='Active'
  &outFields=*
  &f=json

See API Response

Parameters

Parameter	Description	Example
where	SQL-like string of boolean operators	FACUSE like ‘Elementary’ AND ZIP_CODE=20002

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Filter by Location

Example

Single point location:

http://tigerweb.geo.census.gov/arcgis/rest/services/TIGERweb/Places_CouSub_ConCity_SubMCD/MapServer/15/query
    ?outFields=*
    &geometryType=esriGeometryPoint
    &geometry=-77.06930,38.89733
    &inSR=4326
    &f=json

Extent area:

http://maps2.dcgis.dc.gov/dcgis/rest/services/DCGIS_DATA/Education_WebMercator/MapServer/5/query
?where=FACUSE like '%Elementary%' AND TOTAL_STUD >= 200 AND TOTAL_STUD <= 1000
&geometry={"xmin":-77.0036,"ymin":38.8879,"xmax":-76.98434,"ymax":38.90007,"spatialReference":{"wkid":4326}}
&geometryType=esriGeometryEnvelope
&inSR=4326
&outFields=*

Parameters

Parameter	Description	Example
geometryType	Point, Line or Polygon request	esriGeometryPoint
geometry	Longitude, Latitude pair or JSON	-77.06930,38.89733
inSR	Spatial reference of input geometry	4326

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Aggregation Statistics

Examples

Total number of students by school type and number of zipcodes that have this school type:

http://maps2.dcgis.dc.gov/dcgis/rest/services/DCGIS_DATA/Education_WebMercator/MapServer/5/query
  ?groupByFieldsForStatistics=FACUSE,
  &outStatistics= [{
        "statisticType": "sum", 
        "onStatisticField": "TOTAL_STUD", 
        "outStatisticFieldName": "TOTAL_STUD_SUM"
      },{
        "statisticType": "count", 
        "onStatisticField": "ZIP_CODE", 
        "outStatisticFieldName": "ZIP_CODE_COUNT"
      }]
  &where=1=1
  &outFields=*
  &f=json

See API Response

Parameters

Parameter	Description	Example
groupByFieldsForStatistics	Attribute to use as key for aggregation	ZIP_CODE
outStatistics	Array of statistics calculations. Can be one or many	[{"statisticType": "sum", "onStatisticField": "TOTAL_STUD", "outStatisticFieldName": "TOTAL_STUD_SUM"}]
outStatistics.statisticType	Type of Statistic to calculate: count,sum, avg, var, max, min	sum
outStatistics.onStatisticField	Layer attribute to use with statistic type	NUM_STUDENTS
outStatistics.outStatisticFieldName	Name to use for the field	NUM_STUDENTS_SUM