Question

我试图设置一个简单的触发器，当从注册中删除某些内容时，它也会从乐谱和学生表中删除。我觉得我已经正确设置了所有内容，但我一直收到此错误：错误ora-00922：丢失或无效操作。我已经对错误进行了一些研究，但我没有随处可见。我在sql developer中这样做。我是半新的sql所以任何帮助将不胜感激。我的代码如下：

delimiter //
create or replace TRIGGER enrolls_trigger

AFTER DELETE ON ENROLLS

FOR EACH ROW

BEGIN

DELETE FROM scores

WHERE scores.sid= old.sid

AND scores.term = old.term AND scores.lineno = old.lineno

AND scores.compname = old.compname AND scores.points = old.points;

DELETE FROM students

WHERE students.sid = old.sid;

END//

Answer 1

你的语法有点偏。要引用DML事务的先前值，请使用：old。

-- delimiter
CREATE OR REPLACE TRIGGER enrolls_trigger AFTER
    DELETE ON enrolls
    FOR EACH ROW
BEGIN
    DELETE FROM scores
    WHERE
        scores.sid =:old.sid
        AND scores.term =:old.term
        AND scores.lineno =:old.lineno
        AND scores.compname =:old.compname
        AND scores.points =:old.points;

    DELETE FROM students
    WHERE
        students.sid =:old.sid;

END;
--delimiter

此外，如果您正在使用SQL Developer，那么您希望拥有一个＆＃39 ;;＆＃39;在触发器主体上的END关键字之后。

Trigger Docs

为了获得更好的帮助，请包含您的TABLE DDL。我创建了这些以便于使用。

CREATE TABLE enrolls (
    sid        INTEGER,
    term       INTEGER,
    lineno     INTEGER,
    compname   VARCHAR2(10),
    points     INTEGER
);

CREATE TABLE scores (
    sid        INTEGER,
    term       INTEGER,
    compname   VARCHAR2(10),
    points     INTEGER,
    lineno     INTEGER
);

CREATE TABLE students (
    sid   INTEGER
);

Answer 2

我建议采用另一种方法 - 使用ON DELETE CASCADE选项创建的外键约束。看看下面的例子。

感谢Jeff提供了我稍微修改过的CREATE TABLE语句，即只添加了必要的约束。请注意，我只选择SID列作为从SCORES表到ENROLLS的外键。顺便说一下，在SCORES表中重复那么多列的重点是什么？我建议你只保留外键约束列（例如SID），并省略其他列。

最后，我们开始：创建表格：

SQL> CREATE TABLE enrolls (
  2      sid        INTEGER constraint pk_en primary key,
  3      term       INTEGER,
  4      lineno     INTEGER,
  5      compname   VARCHAR2(10),
  6      points     INTEGER
  7  );

Table created.

SQL> CREATE TABLE scores (
  2      sid        INTEGER,
  3      term       INTEGER,
  4      lineno     INTEGER,
  5      compname   VARCHAR2(10),
  6      points     INTEGER,
  7      constraint fk_sco_en foreign key (sid)
  8        references enrolls
  9        on delete cascade
 10  );

Table created.

SQL> CREATE TABLE students (
  2      sid   INTEGER,
  3      constraint fk_stu_en foreign key (sid)
  4        references enrolls
  5        on delete cascade
  6  );

Table created.

SQL>

插入样本数据：

SQL> insert into enrolls  (sid, term) values (100, 1);

1 row created.

SQL> insert into enrolls  (sid, term) values (200, 2);

1 row created.

SQL> insert into scores   (sid, term) values (100, 1);

1 row created.

SQL> insert into scores   (sid, term) values (200, 2);

1 row created.

SQL> insert into students (sid)       values (100);

1 row created.

SQL> insert into students (sid)       values (200);

1 row created.

SQL>
SQL> select * From students;

       SID
----------
       100
       200

SQL> select * From scores;

       SID       TERM     LINENO COMPNAME       POINTS
---------- ---------- ---------- ---------- ----------
       100          1
       200          2

SQL> select * From enrolls;

       SID       TERM     LINENO COMPNAME       POINTS
---------- ---------- ---------- ---------- ----------
       100          1
       200          2

SQL>

现在：如果我从ENROLLS表中删除一行，Oracle将完成其余的工作：

SQL> delete from enrolls where sid = 100;

1 row deleted.

SQL> select * From students;

       SID
----------
       200

SQL> select * From scores;

       SID       TERM     LINENO COMPNAME       POINTS
---------- ---------- ---------- ---------- ----------
       200          2

SQL> select * From enrolls;

       SID       TERM     LINENO COMPNAME       POINTS
---------- ---------- ---------- ---------- ----------
       200          2

SQL>

请参阅？ SID = 100已从所有表中删除，无需任何其他编码（即无需触发）。

错误ora-00922：触发器上的操作丢失或无效

2 个答案: