1.) Location, Call, and Code default to NULL instead of '' (as in innodb).

CREATE TABLE `test_table1` (
`Site` varchar(5) DEFAULT '',
`Location` varchar(55) DEFAULT '',
`Call` varchar(25) DEFAULT '',
`Code` varchar(4) DEFAULT ''
) ENGINE=Columnstore;

INSERT INTO test_table1(Site) VALUES ('tst');

MariaDB [mpcol]> SELECT * FROM test_table1\G
----------------- 1. row ---------------------
Site: tst
Location: NULL
Call: NULL
Code: NULL
1 row in set (0.043 sec)

=================== INNODB ==================================
CREATE TABLE `test_table1_innodb` (
`Site` varchar(5) DEFAULT '',
`Location` varchar(55) DEFAULT '',
`Call` varchar(25) DEFAULT '',
`Code` varchar(4) DEFAULT ''
);

INSERT INTO test_table1_innodb(Site) VALUES ('tst');

SELECT * FROM test_table1_innodb\G
------------------- 1. row --------------------
Site: tst
Location:
Call:
Code:
1 row in set (0.000 sec)

2). Updating a field to an empty string updates the field to NULL

UPDATE test_table1 SET Location='loc';
--------------
Site: tst
Location: loc
Call: NULL
Code: NULL
1 row in set (0.008 sec)

UPDATE test_table1 SET Location='';

MariaDB [my.test]> select * from test_table1\G
----------------------------
Site: tst
Location: NULL
Call: NULL
Code: NULL
1 row in set (0.008 sec)

3). Searching for an empty string returns records with NULL:

select Code from test_table1 where Code=''\G
---------------
Code: NULL
1 row in set (0.008 sec)