Sql 在触发器语句中选择

我有一个触发器：

CREATE OR REPLACE TRIGGER TR_SIGHTING_DESC
BEFORE INSERT ON sightings
FOR EACH ROW
BEGIN
SELECT bird_name
INTO bn
from birds
where bird_id = :new.bird_id;    
    :new.description := 'A bird of the species ' 
                        || bn 
                        || ' was spotted in the ' 
                        || :new.latitude || ','|| :new.longitude 
                        || ' part of the observation area';
END;
/

它一直说它是无效的。我试图从相应的ID中检索bird_name，例如，将其插入到sightings表中：

INSERT INTO sightings (spotter_id, bird_id, latitude,
longitude, sighting_date)
VALUES (2457, 901, -28.0, 152, '09-MAR-2016');

---

您必须声明变量

CREATE OR REPLACE TRIGGER TR_SIGHTING_DESC
BEFORE INSERT ON sightings
FOR EACH ROW
DECLARE bn birds.bird_name%type;
BEGIN
SELECT bird_name
INTO bn
from birds
where bird_id = :new.bird_id;    
    :new.description := 'A bird of the species ' 
                        || bn 
                        || ' was spotted in the ' 
                        || :new.latitude || ','|| :new.longitude 
                        || ' part of the observation area';
END;
/

好OL2200

---

在插入dn之前，必须先声明dn。

标记所使用的dbms。（该代码看起来不像ANSI SQL。）您能分享错误的确切文本吗？未定义

bn

变量。请浏览一些basis plsql教程。