Hello,

I found that the validation rule for "letters only" is

Code:
Is Null OR Not Like "*[!a-z]*"
..but I don't understand why. Why does the expression start and end with an asterix and why is negation used? I would have expected something like this


Code:
Like [a-z] .. combined with some quantifier/repetition symbol.
Could you explain to me how the first expression works?