--!syntax_pg
select 
array['a','b'] a1,
array[array['a','b']] a2,
array[array['a','b'],array['c','d']] a3,
array['a',null] a4,
array[null] a5,
array[1] a6,
array[1,2] a7,
array[null::int4,2] a8,
array[array[1,2]] a9,
array[array[1,2],array[3,4]] a10,
array_out(array[1,2]) a11,
array_out(array[null,'NULL','',',','{}']) a12