Question

I have db in MySQL, with two tables and I need to make query like this

SELECT a.*, b.* from db1.A a1 left join db2.A a2 using(id) where a1.email <> a2.email

So i would like to find guys who has non empty email field in db1.A table and their emails does not match the same guys email from db2.A, and write emails from db1.A to db2.A.

in the beginning we have

db1.A          db2.A
email          email
[e-mail]      NULL

in result ii would like to get

db1.A          db2.A
email          email
[e-mail]      [e-mail]

I can make it with any script language, but can it be done (such tasks) with help only SQL ?

Answer 1

Seems to me it can be easily achieved by next query:

update db2.A a2, db1.A a1 set a2.email=a1.email where a1.id=a2.id and (db2.email is null or db2.email = '') and a1.email <> a2.email;

thanks everyone.