Postgresql 如何在不同的行中显示两列，避免重复并省略空条目

我得到了两个表，我加入了查询. 连接的表有两列，我需要它们作为查询输出中的单独行；必须省略重复项.

到目前为止，我明白了.

如果联接表的第二列中有一列为空，则也必须省略该行. 我不能满足这个要求.

create table article (id integer, artnum varchar(100), artname varchar(100), PRIMARY KEY (artnum));
 insert into article (id, artnum, artname) values (1, '100', 'apple');
 insert into article (id, artnum, artname) values (2, '101', 'banana');
 insert into article (id, artnum, artname) values (3, '102', 'clementine');
 insert into article (id, artnum, artname) values (4, '103', 'dragon fruit');
--
create table supplier (id integer, supartnum varchar(100), supplier1 varchar(100), supplier1name varchar(100), supplier2 varchar(100), supplier2name varchar(100), PRIMARY KEY (supartnum));
 insert into supplier (id, supartnum, supplier1, supplier1name, supplier2, supplier2name) values (1, '100', '23', 'DZ', '42', 'VZ');
 insert into supplier (id, supartnum, supplier1, supplier1name, supplier2, supplier2name) values (2, '101', '42', 'ZV', '23', 'DZ');
 insert into supplier (id, supartnum, supplier1, supplier1name, supplier2, supplier2name) values (3, '102', '23', 'DZ', '', '');
 insert into supplier (id, supartnum, supplier1, supplier1name, supplier2, supplier2name) values (4, '103', '23', 'DZ', '23', 'DZ');

select artnum, artname, --supplier1name, supplier2name,
(unnest(ARRAY(SELECT DISTINCT e FROM unnest(ARRAY[supplier1name,supplier2name]) AS a(e)))) as "suppliercombo"
from article
join supplier on artnum = supartnum
;

结果:

| artnum | artname      | suppliercombo |
| ------ | ------------ | ------------- |
| 100    | apple        | VZ            |
| 100    | apple        | DZ            |
| 101    | banana       | ZV            |
| 101    | banana       | DZ            |
| 102    | clementine   |               |
| 102    | clementine   | DZ            |
| 103    | dragon fruit | DZ            |

首次出现的102号中庭(克莱门汀)与空的供应商组合帽子被省略. 我try 使用UNION，但都失败了，因为它已经是一个300行的SQL，它将被复制.

例子也在DB Fiddle上