mysql - SQL Query to retrieve next available ID from table -

i have table contains column called ticket_id , contains values follows:

ticket_id stk0000000001 stk0000000002 stk0000000001 stk0000000003 stk0000000002 stk0000000001 

the ticket_id value repeat in rows, not unique.

i using query next available id, not able working. returns stk0000000002.

any appreciated!

sql:

select     concat('stk', lpad(seq, 10, '0')) nextid     (select         @seq:=@seq+1 seq,         num             (select             cast(substr(ticket_id, 4) unsigned) num                     sma_support_tickets         union         select             max(cast(substr(ticket_id, 4) unsigned))+2 num                      sma_support_tickets         order             num) ids     cross join          (select @seq:=0) init      ) pairs     seq!=num limit 1 

maybe i'm missing in question, seems should it:

select concat('stk',                lpad(max(substring(ticket_id, 4)) + 1,                     10,                     '0')              )  sma_support_tickets;