DB2 SQL - 在觸發器生成後無法成功插入表

Question

我一直遇到問題，即在附加了觸發器後將值插入表中。 觸發如下：

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 
; 

插入代碼如下：

INSERT INTO follows 
VALUES('Michael_Phelps@uss.net','Michael_Phelps@uss.net'); 

，誤差如下

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. 

謝謝先進！

Answer 1

，我認爲這就是問題所在：

(Select email from Celebrity) <> N.followed_email 

子查詢可能會返回多個行，以便標量操作<>將無法正常工作。 您必須將該條件改爲類似於：

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