Which values fit the two-character pattern?

Question

Accepted Answer

The underscore _ matches exactly one character - not zero, not two, exactly one. '_b' therefore requires a two-character string where the second character is 'b'. 'ab' is the only match: 'a' is too short (no character before b), 'abc' is too long (two characters before b), and '' is empty. People often confuse _ with % and expect it to match any number of characters.