To nitpick.

For '[]' to be valid as an answer SQL should have allowed something like

mychar LIKE '[]dam'

But this offcourse doesnt work. '[]' only work in conjunction with other input. In this case 'a-z'... which offcourse means that if one of the examples had started with a "1" for instance... it would not have been found. Also some international characters wouldnt have worked with 'a-z' either.

Whereas '_' works as is.

/T