=# SELECT * FROM mlg_addr WHERE mlg_addr_id = '';
ERROR:  invalid input syntax for integer: ""
=# SELECT * FROM mlg_addr WHERE mlg_addr_id IS NULL;
 mlg_addr_id | address1 | address2 | city | state | zipcode5 | zipcode4 | country
-------------+----------+----------+------+-------+----------+----------+---------
(0 rows)