PostGIS ST_Difference function returns wrong geometry in result

What is the difference between ST_Contains and ST_Within in PostGIS?

ST_Within(geometry A , geometry B) returns TRUE if the first geometry is completely within the second geometry. ST_Within tests for the exact opposite result of ST_Contains. ST_Contains(geometry A, geometry B) returns TRUE if the second geometry is completely contained by the first geometry.

What is the difference between ST_Contains and ST_Within?

In colloquial terms, ST_Contains determines whether the first geometry given to it encloses the second geometry (whether the first contains the second). ST_Within determines whether the first geometry is completely inside the second (whether the first is within the second).

What is the difference between ST_Crosses and ST_Intersects?

Use ST_Intersects to determine whether two geometries intersect. Use ST_Crosses to determine whether one geometry crosses another. Use ST_Overlaps to determine whether two geometries of the same dimension overlap.

What is difference between geometry and geography in PostGIS?

PostGIS gives you a choice of two different ways to store geospatial data: Geometry, where it assumes all of your data lives on a Cartesian plane (like a map projection); Geography, where it assumes that your data is made up of points on the earth’s surface, as specified by latitudes and longitudes.
 

What is the difference between ST_Contains and ST_Intersects?

ST_Intersects()



This function determines whether or not two geometries share the same space in any way. Unlike ST_Contains(), which tests whether or not one geometry is fully within another, ST_Intersects() looks for intersection between any parts of the geometries.

How does PostGIS store geometry data?

With PostGIS, you can actually store data in a geometry column. This column stores data in a spatial coordinate system that’s defined by an SRID (Spatial Reference Identifier). This allows your database structure to reflect the spatial data that’s stored in the database.

What is the opposite of ST_Contains?

ST_Within is the opposite of ST_Contains. ST_Within(A, B) returns true if geometry A is completely inside geometry B.
 

What is contains in PostGIS?

A contains B if and only if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A. A subtlety of the definition is that a geometry does not contain things in its boundary. Thus polygons and lines do not contain lines and points lying in their boundary.

What is srid 4326?

The SRID is used to tell which spatial reference system will be used to interpret each spatial object. A common SRID in use is 4326, which represents spatial data using longitude and latitude coordinates on the Earth’s surface as defined in the WGS84 standard, which is also used for the Global Positioning System (GPS).

What is the difference between Postgres and PostGIS?

PostGIS is an open source, freely available spatial database extender for the PostgreSQL Database Management System (a.k.a DBMS). So PostgreSQL (a.k.a. Postgres) is THE database and PostGIS is like an add-on to that database. The latest release version of PostGIS now comes packaged with PostgreSQL.