let me give  you a complete example:
suppose a table  of personnel information including the following fields.
id, firstname, lastname, father_name and age.
when you insert  data:
Jack, Smith, adam, 27
it will insert with an integer PK (like 987)
now if you accidentally insert those data  again, it will insert another record  with another PK (like 988) which is not desireable
now what I want is that I want to control generating primary  keys based  on the given data. I need a hash algorithm  which gives numeric  outputs as follows.
JackSmithadam27----->1025458218
JackSmithadam23----->1025498548
JackSmithadam27----->1025458218------->PK exist