ST_ndDWithin函數，判斷指定的兩個對象在指定的座標軸上是否距離小於等於某一給定值。
文法
bool ST_{2D|3D}DWithin(geometry geom, trajectory traj, float8 dist);
bool ST_{2D|3D}DWithin(trajectory traj, geometry geom, float8 dist);
bool ST_{2D|3D}DWithin(geometry geom, trajectory traj, timestamp ts, timestamp te, float8 dist);
bool ST_{2D|3D}DWithin(trajectory traj, geometry geom, timestamp ts, timestamp te, float8 dist);
bool ST_{2D|2DT|3D|3DT}DWithin(boxndf box, trajectory traj, float8 dist);
bool ST_{2D|2DT|3D|3DT}DWithin(trajectory traj, boxndf box, float8 dist);
bool ST_{2D|2DT|3D|3DT}DWithin(boxndf box, trajectory traj, timestamp ts, timestamp te, float8 dist);
bool ST_{2D|2DT|3D|3DT}DWithin(trajectory traj, boxndf box, timestamp ts, timestamp te, float8 dist);
bool ST_{2D|2DT|3D|3DT}DWithin(trajectory traj1, trajectory traj2, float8 dist);
bool ST_{2D|2DT|3D|3DT}DWithin(trajectory traj1, trajectory traj2, timestamp ts, timestamp te, float8 dist);參數
| 參數名稱 | 描述 |
| geom | 需要判斷的幾何對象。 |
| traj | 需要判斷的軌跡對象，或者產生子軌跡的原始軌跡。 |
| traj1 | 需要判斷的軌跡對象，或者產生子軌跡的原始軌跡。 |
| traj2 | 需要判斷的軌跡對象，或者產生子軌跡的原始軌跡。 |
| box | 需要判斷的外包框對象。 |
| ts | 如存在，表示按此時間作為開始時間截取子軌跡。 |
| te | 如存在，表示按此時間作為結束時間截取子軌跡。 |
| dist | 距離的臨界值。 |
描述
- 對於2D和3D的DWithin操作，我們判斷兩者在二維或三維空間上的投影（即對應的geometry類型）是否距離小於等於給定值。
- 對於2DT和3DT的DWithin操作，我們判斷兩者是否在某一時間點上在指定維度上的距離小於等於過給定值。
如果函數包含ts和te參數，表示需要判斷的對象（traj，或traj1和traj2）是在[ts,te]時間段內的子軌跡；如果函數不包含ts和te參數，表示需要判斷的對象（traj，或traj1和traj2）是完整的軌跡。
直接調用ST_DistanceWithin(..)函數相當於調用ST_2DDWithin(...)（若前兩個參數其中一個為幾何對象）或ST_3DTDWithin(...)（若前兩個參數均為軌跡對象）。
樣本
WITH traj AS(
Select ST_makeTrajectory('STPOINT', 'LINESTRING(0 0 10, 50 0 10, 100 0 10)'::geometry,
('[' || ST_PGEpochToTS(0) || ',' || ST_PGEpochToTS(100) || ')')::tsrange,
'{"leafcount":3,"attributes":{"velocity": {"type": "integer", "length": 2,"nullable" : true,"value": [120,130,140]}, "accuracy": {"type": "float", "length": 4, "nullable" : false,"value": [120,130,140]}, "bearing": {"type": "float", "length": 8, "nullable" : false,"value": [120,130,140]}, "acceleration": {"type": "string", "length": 20, "nullable" : true,"value": ["120","130","140"]}, "active": {"type": "timestamp", "nullable" : false,"value": ["Fri Jan 01 11:35:00 2010", "Fri Jan 01 12:35:00 2010", "Fri Jan 01 13:30:00 2010"]}}, "events": [{"2" : "Fri Jan 02 15:00:00 2010"}, {"3" : "Fri Jan 02 15:30:00 2010"}]}') a,
ST_makeTrajectory('STPOINT', 'LINESTRING(0 20, 50 20, 100 20)'::geometry,
('[' || ST_PGEpochToTS(0) || ',' || ST_PGEpochToTS(100) ||')')::tsrange,
'{"leafcount":3,"attributes":{"velocity": {"type": "integer", "length": 2,"nullable" : true,"value": [120,130,140]}, "accuracy": {"type": "float", "length": 4, "nullable" : false,"value": [120,130,140]}, "bearing": {"type": "float", "length": 8, "nullable" : false,"value": [120,130,140]}, "acceleration": {"type": "string", "length": 20, "nullable" : true,"value": ["120","130","140"]}, "active": {"type": "timestamp", "nullable" : false,"value": ["Fri Jan 01 11:35:00 2010", "Fri Jan 01 12:35:00 2010", "Fri Jan 01 13:30:00 2010"]}}, "events": [{"2" : "Fri Jan 02 15:00:00 2010"}, {"3" : "Fri Jan 02 15:30:00 2010"}]}') b
)
SELECT ST_2dDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(49), 19), ST_3dDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(49), 19),
ST_2dDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(50), 20), ST_3dDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(50), 20),
ST_2dDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(70), 21), ST_3dDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(70), 21),
ST_2dtDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(49), 19), ST_3dtDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(49), 19),
ST_2dtDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(50), 20), ST_3dtDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(50), 20),
ST_2dtDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(70), 21), ST_3dtDWithin(a,b, ST_PGEpochToTS(0),ST_PGEpochToTS(70), 21) from traj;
NOTICE: One or both of the geometries is missing z-value. The unknown z-value will be regarded as "any value"
NOTICE: One or both of the geometries is missing z-value. The unknown z-value will be regarded as "any value"
st_2ddwithin | st_3ddwithin | st_2ddwithin | st_3ddwithin | st_2ddwithin | st_3ddwithin | st_2dtdwithin | st_3dtdwithin | st_2dtdwithin | st_3dtdwithin | st_2dtdwithin | st_3dtdwithin
--------------+--------------+--------------+--------------+--------------+--------------+---------------+---------------+---------------+---------------+---------------+---------------
f | f | t | t | t | t | f | f | t | t | t | t