Converts the geometry to a compound curve.
Syntaxgeometry-expression.ST_ToCompound() ReturnsST_CompoundCurve If the geometry-expression is of type ST_CompoundCurve, return the geometry-expression. If the geometry-expression is of type ST_LineString or ST_CircularString, return a compound curve containing one element, the geometry-expression. If the geometry-expression is a geometry collection with a single element of type ST_Curve, return that element cast as ST_CompoundCurve. If the geometry-expression is the empty set, return an empty set of type ST_CompoundCurve. Otherwise, raise an exception condition.
The spatial reference system identifier of the result is the same as the spatial reference system of the geometry-expression.
RemarksConverts the geometry to a circularstring. The logic is equivalent to that used for CAST( geometry-expression AS ST_CompoundCurve ).
If geometry-expression is already known to be an ST_CompoundCurve value, it is more efficient to use TREAT( geometry-expression AS ST_CompoundCurve ) than the ST_ToCompound method.
By default, ST_ToCompound uses the original format for a geometry, if it is available. Otherwise, the internal format is used. For more information about internal and original formats, see STORAGE FORMAT clause, CREATE SPATIAL REFERENCE SYSTEM statement.
See also Standards and compatibilitySQL/MM (ISO/IEC 13249-3: 2006) 5.1.33
ExampleThe following example returns the result CompoundCurve ((0 0, 2 1)).
SELECT NEW ST_LineString( 'LineString( 0 0, 2 1 )' ).ST_ToCompound() |
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