insert into tb1 (val1, val2) select (val1, val2) from tb2, null value issue

[blackhorse]

I am using subquery to insert data like this.

insert into tb1 (val1, val2) select (val1, val2) from tb2

val1 or val2 in tb2 are string and they could be NULL value. But in tb1, I don't want to have null values. I want like if val1 and/or val2 in tb2 are null values, when i insert them into tb1, I want to save them as ''.

How could I do that in MySQL?

Thanks!

[dagon]

11.3. Control Flow Functions