Getting the last word from a Postgres string, declaratively

Question

[EDIT] original title of this question was \"Getting the last element of a Postgres array, declaratively\"

How to obtain the last element of the array in Postgr

Answer 1

Edited: THIS IS WRONG -- SEE BELOW FOR CORRECT ANSWER --

I guess you must use array_length() :

SELECT string_to_array('hi guys, welcome', ' ') AS arr INTO temparr;
SELECT * FROM temparr;
         arr
----------------------
 {hi,"guys,",welcome}

SELECT arr[array_length(arr,1)] FROM temparr;
   arr
---------
 welcome

To use this declaratively, (on the fly) you can create a little SQL function:

CREATE FUNCTION last_elem (text[]) RETURNS text AS $$
 SELECT $1[array_length($1,1)];
$$ LANGUAGE SQL;


 select last_elem(string_to_array('hi guys, welcome', ' '));
 last_elem
-----------
 welcome

------- EDITED -- CORRECT ANSWER FOLLOWS ----------------------

The above is not correct because in Postgresql arrays can sometimes be not one-based.

The correct way, then, is with array_upper()

CREATE FUNCTION last_elem (text[]) RETURNS text AS $$
 SELECT $1[array_upper($1,1)];
$$ LANGUAGE SQL;


 select last_elem(string_to_array('hi guys, welcome', ' '));
 last_elem
-----------
 welcome