fungsi st_force2d

Berlaku untuk: Databricks Runtime 18.1 ke atas

Penting

Fitur ini ada di Pratinjau Umum.

Mengembalikan proyeksi 2D dari input GEOGRAPHY atau GEOMETRY nilai.

Sintaksis

st_force2d ( geoExpr )

Argumen

• geoExpr: Nilai GEOGRAPHY atau GEOMETRY.

Pengembalian Barang

Nilai jenis GEOGRAPHY atau GEOMETRY, yang mewakili proyeksi 2D dari nilai input.

Nilai SRID dari output GEOGRAPHY atau GEOMETRY nilai sama dengan nilai input.

Fungsi mengembalikan NULL jika input adalah NULL.

Catatan

Jika input memiliki koordinat Z atau M, ini dikecualikan dalam output.

Jika input sudah 2D, fungsi mengembalikannya tidak berubah.

Examples

-- Drops the M coordinate from a point geography.
> SELECT st_astext(st_force2d(st_geogfromtext('POINT M (1 2 3)')));
  POINT(1 2)
-- Drops Z and M coordinates from a multipoint geography.
> SELECT st_astext(st_force2d(st_geogfromtext('MULTIPOINT ZM (EMPTY,0 0 10 20, 1 1 11 21)')));
  MULTIPOINT(EMPTY,(0 0),(1 1))
-- Drops the Z coordinate from a polygon geography.
> SELECT st_astext(st_force2d(st_geogfromtext('POLYGON Z ((0 0 2,1 0 3,0 1 4,0 0 5))')));
  POLYGON((0 0,1 0,0 1,0 0))
-- Drops the Z coordinate from a point geometry.
> SELECT st_astext(st_force2d(st_geomfromtext('POINT Z (1 2 3)')));
  POINT(1 2)
-- Drops Z and M coordinates from a linestring geometry.
> SELECT st_astext(st_force2d(st_geomfromtext('LINESTRING ZM (0 0 10 20, 1 1 11 21)')));
  LINESTRING(0 0,1 1)
-- Returns the input 2D geometry as is.
> SELECT st_astext(st_force2d(st_geomfromtext('POINT(1 2)')));
  POINT(1 2)
-- Preserves the SRID of the input geography.
> SELECT st_srid(st_force2d(st_geogfromtext('POINT(1 2)')));
  4326
-- Preserves the SRID of the input geometry.
> SELECT st_srid(st_force2d(st_geomfromtext('POINT(1 2)', 4326)));
  4326
-- Returns NULL if the input is NULL.
> SELECT st_force2d(NULL);
   NULL

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