Show difference between mySQL tables
Left join where there is no match on the left (IS NULL):

SELECT campaign_id as id, tbl1.nickname as name
FROM tbl1
LEFT JOIN tbl2 ON nickname=name
WHERE tbl2.id IS NULL


Alternately there is a MariaDB-10.3 syntax:




select version();



| version()                                   |
| :------------------------------------------ |
| 10.3.11-MariaDB-1:10.3.11+maria~stretch-log |






create table tbl1 (name varchar(20))



✓






insert into tbl1 values ('n1'),('n2'),('n6')



✓






create table tbl2 (name varchar(20))



✓






insert into tbl2 values ('n1'),('n2'),('n12')



✓






select name from tbl1 except select name from tbl2



| name |
| :--- |
| n6   |



db&lt;>fiddle here