Constraint Query Language¶
The Constraint Query Language is used to define expressions and filters in several parts of the uDig application.
The CQL syntax is defined as part of the OGC Catalog specification (in much the same way the well-known-text representation of geometry is defined as part of the Simple Feature for SQL specification).
Filters¶
A Filters is used to test content, similar in spirit to a WHERE statement in SQL. Filters are used to define the selected Features in a uDig layer.
Comparisons¶
CITY = 'Nelson'
ATTR1 < (1 + ((2 / 3) * 4))
ATTR1 < abs(ATTR2)
ATTR1 < 10 AND ATTR2 < 2 OR ATTR3 > 10
Between¶
ATTR1 BETWEEN 10 AND 20
Spatial Relationships¶
CONTAINS(ATTR1, POINT(1 2))
CROSS(ATTR1, LINESTRING(1 2, 10 15))
INTERSECT(ATTR1, GEOMETRYCOLLECTION (POINT (10 10),POINT (30 30),LINESTRING (15 15, 20 20)) )
BBOX(ATTR1, 10,20,30,40)
DWITHIN(ATTR1, POINT(1 2), 10, kilometers)
BBOX(ATTR1, 10,20,30,40)
Time¶
Before a date.
ATTR1 BEFORE 2006-11-30T01:30:00Z
Before a period
ATTR1 BEFORE 2006-11-30T01:30:00Z/2006-12-31T01:30:00Z
After a date.
ATTR1 AFTER 2006-11-30T01:30:00Z
After a period
ATTR1 AFTER 2006-11-30T01:30:00Z/2006-12-31T01:30:00Z
Temporal predicate with dutation (ten day after 2006-11-30T01:30:00Z )
ATTR1 AFTER 2006-11-30T01:30:00Z/P10D
ATTR1 AFTER 2006-11-30T01:30:00Z/T10H
During predicate
ATTR1 DURING 2006-11-30T01:30:00Z/2006-12-31T01:30:00Z
Compound Attributes¶
gmd:MD_Metadata.gmd:identificationInfo.gmd:MD_DataIdentification.gmd:abstract LIKE 'abc%'
Expressions¶
Expressions are used to extract a value similar in spirit to a SELECT statement in SQL. Unlike SQL expressions are strictly untyped; the following produces the same result:
- sin( 0 )
- sin( 0.0 )
- sin( ‘0’ )
In many cases you will see several functions defined with similar names; differing only in how they interpret the provided argument expressions. The functions functions that produce a boolean value are very similar to a filter.
Functions¶
sin( pi() / 4 )
sin( toRadians( ANGLE ) )
getX( pointN( THE_GEOM, 0 ) )
area( THE_GEOM )
ID()
Function List:
double Area(Geometry) // alternate implementation
double area(Geometry)
long abs( number ) // number treated as long
double abs_2( number ) // number treated as double
float abs_3( number ) // number treated as float
int abs_4( number ) // number treated as int
double acos( cos )
double asin( sin )
double atan( tan )
double atan2( x, y ) // convert x, y to theta
boolean between( value, min, max )
boundary(Geometry)
boundaryDimension(Geometry)
buffer(Geometry, double)
bufferWithSegments(Geometry, double, int)
double ceil( number )
centroid(Geometry)
contains(Geometry, Geometry)
convexHull(Geometry)
double cos( radians )
crosses(Geometry, Geometry)
difference(Geometry, Geometry)
dimension(Geometry)
disjoint(Geometry, Geometry)
distance(Geometry, Geometry)
double2bool(double)
endPoint(Geometry)
envelope(Geometry)
equalsExact(Geometry, Geometry)
equalsExactTolerance(Geometry, Geometry, double)
equalTo(Object, Object)
double exp( number )
exteriorRing(Geometry)
double floor( number )
String geometryType(Geometry)
Geometry geomFromWKT(String)
double geomLength(Geometry)
Geometry getGeometryN(Geometry, int)
double getX( Point )
double getY( Point )
boolean greaterEqualThan(Object, Object)
boolean greaterThan(Object, Object)
double IEEEremainder( dividend, divisor )
value if_then_else(boolean, value, value )
in2(value, Object, Object) // tests to is if value is equal to one of the listed objects
in3(value, Object, Object, Object)
in4(value, Object, Object, Object, Object)
in5(value, Object, Object, Object, Object, Object)
in6(value, Object, Object, Object, Object, Object, Object)
in7(value, Object, Object, Object, Object, Object, Object, Object)
in8(value, Object, Object, Object, Object, Object, Object, Object, Object)
in9(value, Object, Object, Object, Object, Object, Object, Object, Object, Object)
in10(value, Object, Object, Object, Object, Object, Object, Object, Object, Object, Object)
boolean int2bbool(int)
double int2ddouble(int)
Point interiorPoint(Geometry)
LinearRing interiorRingN(Geometry, int)
Geometry intersection(Geometry, Geometry)
boolean intersects(Geometry, Geometry)
boolean isClosed(Geometry)
boolean isEmpty(Geometry)
isLike(String, String)
isNull(Object)
isRing(Geometry)
isSimple(Geometry)
isValid(Geometry)
isWithinDistance(Geometry, Geometry, double)
lessEqualThan(Object, Object)
lessThan(Object, Object)
double log( number )
double max( number, number )
float max_2( number, number )
int max_3( number, number )
long max_4( number, number )
double min( number, number )
float min_2( number, number )
int min_3( number, number )
long min_4( number, number )
not(boolean)
notEqualTo(Object, Object)
numGeometries(Geometry)
numInteriorRing(Geometry)
numPoints(Geometry)
overlaps(Geometry, Geometry)
parseBoolean(String)
parseDouble(String)
parseInt(String)
pointN(Geometry, int)
double pow( base, exponent )
double random()
String relate(Geometry, Geometry)
boolean relatePattern(Geometry, Geometry, String)
double rint( number ) // closest integer
int round( number )
long round_2( number )
int roundDouble( number ) // number is treated as a double
double sin( radians )
double sqrt( number )
startPoint(Geometry)
strConcat(String, String)
strEndsWith(String, String)
strEqualsIgnoreCase(String, String)
strIndexOf(String, String)
strLastIndexOf(String, String)
strLength(String)
strMatches(String, String)
strStartsWith(String, String)
strSubstring(String, int, int)
strSubstringStart(String, int)
strTrim(String)
symDifference(Geometry, Geometry)
double tan( radians )
touches(Geometry, Geometry)
double toDegrees( radians )
double toRadians( degrees )
String toWKT(Geometry)
union(Geometry, Geometry)
within(Geometry, Geometry)
Extended CQL¶
The common query language cannot quite do everything we would like it to. The following extensions are not strictly common query language (so please do not expect them to work with other applications).
Feature ID¶
You can select against a feature identifier using:
IN ('river.1', 'river.2')
Or if you have an integer type as feature id:
IN (300, 301)
Related tasks
Related reference