Update db.sql

FIXED: ERROR 1071 (42000) at line 8: Specified key was too long; max key length is 767 bytes.

The number of allowed characters just depends on your character set. UTF8 may use up to 3 bytes per character, utf8mb4 up to 4 bytes, and latin1 only 1 byte. Thus for utf8 your key length is limited to 255 characters, since 3*255 = 765 < 767

Please refer: http://stackoverflow.com/a/16820166/782094