MYSQL update if not exists else do nothing -

my question how update value in table if not exists on table.i checked insert ... on duplicate key update describes inserting updates , not insert.

my situation like, have 2 tables (t1,t2). want update column in t1 value if not present in t2. otherwise increment value , try update again. want like

update t1 set column = 'value' if not exists in t2 

can suggest solution

here way using join.

create table tab1 (id int , val int); insert tab1 values (1,1),(2,3),(3,5);  create table tab2 (id int , val int); insert tab2  values (4,1),(2,3),(3,5); 

in above tab1 (id = 1) not available in tab2 , using following command can update such values

update tab1 t1 left join tab2 t2 on t1.id = t2.id  set t1.val =    case      when t2.id null  8      else t1.val   end 

the output after update command like

mysql> select * tab1 ; +------+------+ | id   | val  | +------+------+ |    1 |    8 | |    2 |    3 | |    3 |    5 | +------+------+ 

also can use exist pretty better doing left join

update tab1 t1 set t1.val = 10 not exists (   select 1   tab2 tab2.id = t1.id )