Not really; that selects anything except a row with an upper-case letter
in the first column and a lower-case letter in the second.  So, for
example, it collects "aZ" as invalid; it also does not reject
"Hammer-Anvil"; it rejects "09" which is all alphanumeric.

The question is a bit harder than it looks - doubly so if the 'text
column' is a column of type TEXT (classic text blob).  Assuming a
regular character string type, you need to use:

SELECT text_col FROM source WHERE text_col MATCHES "*[^A-Za-z0-9]*";

This searches for a string of zero or more of any sort of character,
followed by a non-alphanumeric, followed by another string of zero or
more of any sort of character.

I think that fails on a TEXT column - but try it anyway.