Returns the geometry value that represents the point set intersection of two geometries.
SELECT NEW ST_Polygon( 'Polygon( (-1 -0.25, 1 -0.25, 1 2.25, -1 2.25, -1 -0.25) )' ) AS A , NEW ST_CurvePolygon( 'CurvePolygon( CircularString( 0 1, 1 2, 2 1, 1 0, 0 1 ) )' ) AS B , A.ST_Intersection( B ) AS C
The intersection is shaded in the following picture. It is a single surface that includes all of the points that are in the square and also in the circle. Union of a square and a circle
SQL/MM (ISO/IEC 13249-3: 2006) 5.1.18