Remind some useful MySQL Query

# Dealing with network, IP address
SELECT substring_index('10.1.2.3', '.', 2);
# Return 10.1

# CONCAT with separator
select concat_ws(' ', 'Anh', 'yeu', 'em') as ixu;

# GROUP_CONCAT with separator
select k, group_concat(v order by v asc separator '; ') as alias
from
  (select 1 as k, 'One' as v
  UNION
  select 1, 'First') t;