words=> select version();
version
----------------------------------------------------------------------------------------------------------
PostgreSQL 9.6.2 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5
20150623 (Red Hat 4.8.5-11), 64-bit
(1 row)
words=> select unnest(ARRAY['a','b','c','d','e','f']) order by random();
unnest
--------
a
b
c
d
e
f
(6 rows)