How can I add the array to the array of arrays in SQL (Postgres)

Question

I have a table with an attribute that is an array of arrays.

Example: a={{1,A, 1},{A,B,C},{45,46,47}}

I want to add an array to the array "a".

Example: new_array={Z,T} to "a" in order to have a={{Z,T},{1,A, 1},{A,B,C},{45,46,47}} `

I used the command: update test set a = ARRAY['Z','T'] || a;

but I got this error: No operator matches the given name and argument type(s). You might need to add explicit type casts.

So, I tried to add the ::text[] parameter in this way: update test set a = ARRAY['Z','T']::text[] || a::text[]; but there is still an error:

ERROR:  cannot concatenate incompatible arrays
DETAIL:  Arrays with differing dimensions are not compatible for concatenation.

Hence, my question is: how can I add the array to the array of arrays? .

Answer 1

To make them the same dimention add a null:

select '{{1,A, 1},{A,B,C},{45,46,47}}'::text[] || '{Z, T, null}';
                ?column?                 
-----------------------------------------
 {{1,A,1},{A,B,C},{45,46,47},{Z,T,NULL}}