By default YSQL will display NULL as an empty string which makes it impossible to distinguish NULL from a true empty string (i.e. ”) or a sequence of blanks.
If you want to quickly identify NULLs in your result set, try this:
yugabyte=# CREATE TABLE some_data (c VARCHAR);
CREATE TABLE
yugabyte=# INSERT INTO some_data VALUES ('A'), ('B'), (NULL), ('D'), ('E'), (NULL);
INSERT 0 6
yugabyte=# SELECT c FROM some_data;
c
---
E
B
D
A
(6 rows)
yugabyte=# \pset null '(NULL)'
Null display is "(NULL)".
yugabyte=# SELECT c FROM some_data;
c
--------
E
B
(NULL)
D
A
(NULL)
(6 rows)
Have Fun!