CHR

Return the character for a given code point (Unicode code points for UTF8).

CHR(int)
For example:
premdb=# SELECT CHR(90);
 chr 
-----
 Z
(1 row)

premdb=# SELECT seasonid, CHR(seasonid) 
FROM season ORDER BY seasonid;

 seasonid |   chr    
----------+----------
        1 | \x01
        2 | \x02
        3 | \x03
        4 | \x04
        5 | \x05
...