sql - MySQL Conditional Update in same table -

i'm looking simple way update on table if there no other columns present in same table same value i'm trying update, ideally in single query. far i'm getting error you specify target table 't1' update in clause. here tried in few variations far (still unable working):

update emailqueue t1  set      t1.lockedon = 1470053240     (select              count(*)                     emailqueue t2                     t2.lockedon = 1470053240) = 0         , t1.lockedon null 

in mysql, need use join. in case, left join in order:

update emailqueue eq left join        emailqueue eq2        on eq2.lockedon = 1470053240     set eq.lockedon = 1470053240 eq.lockedon null ,       eq2.lockedon null;