Question

I have been running into problems inserting values into a table after having a trigger attached to it.
The trigger is the following:

CREATE TRIGGER trig
AFTER INSERT ON Follows
REFERENCING NEW as N
FOR EACH row
WHEN ((Select email from Celebrity) <> N.followed_email)
UPDATE followSuggestion SET followSuggestion.Suggested_follower = N.followed_email, followSuggestion.Suggested_followee = N.follower_email
;

the insert code is the following:

INSERT INTO follows
VALUES('[e-mail]','[e-mail]');

And the error is as follows

DB21034E  The command was processed as an SQL statement because it was not a 
valid Command Line Processor command.  During SQL processing it returned:
SQL0811N  The result of a scalar fullselect, SELECT INTO statement, or VALUES 
INTO statement is more than one row.  SQLSTATE=21000

SQL0811N  The result of a scalar fullselect, SELECT INTO statement, or VALUES INTO statement is more than one row.

Thank you in advanced!

Answer 1

I think this is the problem:

 (Select email from Celebrity) <> N.followed_email

The subquery will probably return more than one row so the scalar operator <> will not work.
You will have to rephrase that condition to something like:

WHEN ((Select COUNT(email) from Celebrity WHERE email = N.followed_email) = 0) ...