Find_SRID — Returns the SRID defined for a geometry column.
integer Find_SRID(varchar a_schema_name, varchar a_table_name, varchar a_geomfield_name);
Returns the integer SRID of the specified geometry column by searching through the GEOMETRY_COLUMNS table. If the geometry column has not been properly added (e.g. with the AddGeometryColumn function), this function will not work.