Fetch and match data from 2 tables?

[Yumi]

2 tables A and B
[...]
column A [...] column B?

Trying to treat tables as columns may be your problem...

Assuming you meant 'table' throughout, there may be a few ways to write the SQL. Perhaps the most obvious is a correlated query:

SELECT tid FROM A WHERE tid NOT IN (SELECT tid FROM B)

If the tid columns are unique, a join could also work:

SELECT A.tid FROM A
LEFT JOIN B ON A.tid=B.tid
WHERE B.tid IS NULL