Exploding a list in Hive SQL to identify blanks - arrays

Question

I have a column called part_nos_list as array<\string> in a hive table. Apparently that column has blank and I want to update that with a '-'. The code sort of does that but 42 rows in a group by has shown having blanks. I tried to check individual records but am not successful. Here is the hive sql. Is there something wrong here in this sql
SELECT order_id, exploded_part_nos
FROM sales.order_detail LATERAL VIEW explode(part_no_list) part_nos AS exploded_part_nos where sale_type in ('POS', 'OTC' , 'CCC') and exploded_part_nos = ''
However this group by sql shows 42 as blanks
select * from (SELECT explo,count(*) as uni_explo_cnt
FROM sales.order_detail
LATERAL VIEW explode(split(concat_ws("##", part_no_list),'##')) yy AS explo where sale_type in ('POS', 'OTC' , 'CCC') group by explo order by explo asc) DD
Here is what hive table looks like
Id Part_no_list
1 ["OTC","POS","CCC"]
2 ["OTC","POS"]
4 NULL
5
6 ["-"]
7 ["OTC","POS","CCC"]
Thanks in advance

Answer 1

To test if exploded array element is empty, use this:
select * from(
select explode( array("OTC","POS","CCC","")) as explo
) s where explo=''
Result is one empty string.
If you want to identify array containing empty element use array_contains:
select * from(
select array("OTC","POS","CCC","") as a
) s where array_contains(a,'')
Result:
["OTC","POS","CCC",""]
If you want to find array containing only one element - empty string use size(array)=1 or array_contains(array,'')
But there is also such thing as an empty array.
It displayed the same as array containing empty element but it is not the same.
And to find empty array, use size()=0
Example:
select * from(
select array() as a
) s where size(a)=0
Returns []
Run all these queries on your data and you will become enlightened. I think it is empty arrays, not empty element in your case
Empty array is not NULL, because it is still an array object of zero size:
select * from(
select array() as a
) s where a is null
Returns no rows
Better query array only without explode and use array_contains and size to find empty arrays and empty elements. Use LATERAL VIEW OUTER to generate rows even when a LATERAL VIEW usually would not generate a row. LATERAL VIEW without OUTER word works as INNER JOIN, see docs about LATERAL VIEW OUTER