STIntersects (geography Data Type)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Returns 1 if a geography instance intersects another geography instance. Returns 0 if it does not.
Syntax
.STIntersects ( other_geography )
Arguments
other_geography
Is another geography instance to compare to the instance on which STIntersects() is invoked.
Return Types
SQL Server return type: bit
CLR return type: SqlBoolean
Remarks
This method always returns NULL if the spatial reference IDs (SRIDs) of the geography instances do not match.
Examples
The following example uses STIntersects() to determine whether two geography instances intersect each other.
DECLARE @g geography;
DECLARE @h geography;
SET @g = geography::STGeomFromText('POLYGON((-122.358 47.653, -122.348 47.649, -122.348 47.658, -122.358 47.658, -122.358 47.653))', 4326);
SET @h = geography::STGeomFromText('LINESTRING(-122.360 47.656, -122.343 47.656)', 4326);
SELECT CASE @g.STIntersects(@h)
WHEN 1 THEN '@g intersects @h'
ELSE '@g does not intersect @h'
END;