Question

Let’s say I have two table table_new and table_old

table_old

ID      email_address  full_name  address
-----------------------------------------
1       [e-mail]        john      street 1
2       [e-mail]        peter     street 2
3       [e-mail]        david     street 3

table_new

ID      email_address
----------------------
1       [e-mail]
2       [e-mail]
3       [e-mail]
4       [e-mail]
5       [e-mail]
...     ....
300     [e-mail]

Questions :

How do I copy the email address from table_new to table_old with some statement below

1. If in table_old already exists an email address from table_new ignore it.
2. If in table_new does not exists an email address from table_old delete it.

So the result should be

table_old

ID      email_address  full_name  address
-----------------------------------------
1       [e-mail]        peter     street 2
2       [e-mail]        david     street 3
3       [e-mail]
4       [e-mail]
5       [e-mail]
...     ....
300     [e-mail]

Let me know.

Answer 1

I guess it can be done in two queries.

delete from old_table where email_address not in 
(select email_address from new_table)

Insert into old_table (email_address) select email_address 
from new_table where email_address not in (select email_address from old_table)

Assuming id is an autoincrement key, otherwise id can be inserted and selected, along with email address.