Is there a better way to calculate the median (not average)

Question

Suppose I have the following table definition:

CREATE TABLE x (i serial primary key, value integer not null);

I want to calculate the MEDIAN o

Answer 1

CREATE TABLE array_table (id integer, values integer[]) ;

INSERT INTO array_table VALUES ( 1,'{1,2,3}');
INSERT INTO array_table VALUES ( 2,'{4,5,6,7}');

select id, values, cardinality(values) as array_length,
(case when cardinality(values)%2=0 and cardinality(values)>1 then (values[(cardinality(values)/2)]+ values[((cardinality(values)/2)+1)])/2::float 
 else values[(cardinality(values)+1)/2]::float end) as median  
 from array_table

Or you can create a function and use it any where in your further queries.

CREATE OR REPLACE FUNCTION median (a integer[]) 
RETURNS float AS    $median$ 
Declare     
    abc float; 
BEGIN    
    SELECT (case when cardinality(a)%2=0 and cardinality(a)>1 then 
           (a[(cardinality(a)/2)] + a[((cardinality(a)/2)+1)])/2::float   
           else a[(cardinality(a)+1)/2]::float end) into abc;    
    RETURN abc; 
END;    
$median$ 
LANGUAGE plpgsql;

select id,values,median(values) from array_table