DB2 SQL - 在触发器生成后无法成功插入表

Question

我一直遇到问题，即在附加了触发器后将值插入表中。 触发如下：

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 
; 

插入代码如下：

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

，误差如下

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. 

谢谢先进！

Answer 1

，我认为这就是问题所在：

(Select email from Celebrity) <> N.followed_email 

子查询可能会返回多个行，以便标量操作<>将无法正常工作。 您必须将该条件改为类似于：

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