ST_attrName-AnalyticDB(AnalyticDB)-阿里云帮助中心

Returns the name of a trajectory attribute field, or the names of all trajectory attribute fields.

Syntax

text[] ST_attrName(trajectory traj);
text ST_attrName(trajectory traj, integer index);

The first overload returns all attribute field names as a text[] array. The second returns a single name by its 0-based index.

Parameters

Parameter	Description
`traj`	The trajectory object.
`index`	The attribute index. Indexing starts at 0.

Examples

Example 1: Return all attribute names

With traj AS (
  select '{"trajectory":{"version":1,"type":"STPOINT","leafcount":2,"start_time":"2010-01-01 11:30:00","end_time":"2010-01-01 12:30:00","spatial":"SRID=4326;LINESTRING(1 1,3 5)","timeline":["2010-01-01 11:30:00","2010-01-01 12:30:00"],"attributes":{"leafcount":2,"velocity":{"type":"integer","length":4,"nullable":true,"value":[1,null]},"speed":{"type":"float","length":8,"nullable":true,"value":[null,1.0]},"angle":{"type":"string","length":64,"nullable":true,"value":["test",null]}, "tngel2":{"type":"timestamp","length":8,"nullable":true,"value":["2010-01-01 12:30:00",null]},"bearing":{"type":"bool","length":1,"nullable":true,"value":[null,true]}}}}'::trajectory a)
Select st_attrName(a) from traj;
              st_attrname
---------------------------------------
 {velocity,speed,angle,tngel2,bearing}
(1 row)

Example 2: Return attribute name by index

The index parameter is 0-based. Index 0 corresponds to the first attribute field.

With traj AS (
  select '{"trajectory":{"version":1,"type":"STPOINT","leafcount":2,"start_time":"2010-01-01 11:30:00","end_time":"2010-01-01 12:30:00","spatial":"SRID=4326;LINESTRING(1 1,3 5)","timeline":["2010-01-01 11:30:00","2010-01-01 12:30:00"],"attributes":{"leafcount":2,"velocity":{"type":"integer","length":4,"nullable":true,"value":[1,null]},"speed":{"type":"float","length":8,"nullable":true,"value":[null,1.0]},"angle":{"type":"string","length":64,"nullable":true,"value":["test",null]}, "tngel2":{"type":"timestamp","length":8,"nullable":true,"value":["2010-01-01 12:30:00",null]},"bearing":{"type":"bool","length":1,"nullable":true,"value":[null,true]}}}}'::trajectory a)
Select st_attrName(a, 0) from traj;
 st_attrname
-------------
 velocity
(1 row)