I'm creating a database in db2 and I want to add a constrain to validate whether the user inserting a valid email address, that contain %@%.% . Without luck...any advice?
You can use LIKE with wildcards. See here for the wildcards on DB2.
The underscore character ( _ ) represents any single character.
The percent sign character (%) represents a string of zero or more characters.
SELECT email
FROM YourTable
WHERE email NOT LIKE '%_@__%.__%'
This will ignore the following cases (simple version for valid emails):
You can see an example in MySql in sqlfiddle.
To add it as a constraint, you do (as mustaccio said in a comment):
alter table your_table add constraint chk_email check (email like '%_@__%.__%')