oracle觸發器上的編譯錯誤

Question

我有一個具有雇員的表（oracle SQL），其中每個雇員都有一個經理（表示為另一個雇員的fk）。 我想創建一個觸發器，當刪除雇員時，在其經理字段中具有其鍵的所有雇員都將其經理更改為null（或-1，或某些保留值）。 我在弄清楚當前代碼出了什么問題時遇到了一些麻煩：

編輯：我修復了我的大部分代碼，並且我正以錯誤的方式進行操作。 我使用了建議的ON DELETE選項，現在一切正常。 這是我的代碼：

CREATE TABLE EmployeeA
(
    employeeID integer,
    firstName varchar (255),
    lastName varchar (255),
    phone integer,
    jobTitle varchar (255),
    payGrade integer,
    fk_EmployeeemployeeID integer,
    PRIMARY KEY(employeeID),
    FOREIGN KEY(fk_EmployeeemployeeID) REFERENCES EmployeeA (employeeID) ON DELETE SET NULL
);
INSERT INTO EMPLOYEEA VALUES (1, null, 'Powell', 0, 'President', 100, 1);
INSERT INTO EMPLOYEEA VALUES (2, null, 'Hicke', 0, 'Dean (Natural Science)', 100, 1);
INSERT INTO EMPLOYEEA VALUES (3, null, 'Fenves', 0, 'Dean (Engineering)', 100, 1);
INSERT INTO EMPLOYEEA VALUES (4, null, 'Porter', 0, 'Chairman (Computer Science)', 100, 2);
INSERT INTO EMPLOYEEA VALUES (5, null, 'Beckner', 0, 'Chairman (Mathematics)', 100, 2);
INSERT INTO EMPLOYEEA VALUES (6, null, 'Miranker', 0, 'Professor (Computer Science)', 100, 4);
INSERT INTO EMPLOYEEA VALUES (7, null, 'Mok', 0, 'Professor (Computer Science)', 100, 4);
DELETE FROM employeeA WHERE lastName = 'Porter'; 

Answer 1

您不想在這里使用觸發器。 使用外鍵的on delete屬性。 定義外鍵約束時，可以指定希望其在刪除父行時將子行設置為NULL 。

SQL> ed
Wrote file afiedt.buf

  1  create table employee2(
  2    employee_id number primary key,
  3    manager_id  number,
  4    employee_first_name varchar(30),
  5    constraint fk_manager_emp
  6      foreign key( manager_id )
  7      references employee2( employee_id )
  8      on delete set null
  9* )
SQL> /

Table created.

如果添加老板，經理（向老板報告）和員工（向經理報告）

SQL> insert into employee2( employee_id, manager_id, employee_first_name )
  2    values( 1, null, 'Boss' );

1 row created.

SQL> ed
Wrote file afiedt.buf

  1  insert into employee2( employee_id, manager_id, employee_first_name )
  2*   values( 2, 1, 'Emp1' )
SQL> /

1 row created.

SQL> ed
Wrote file afiedt.buf

  1  insert into employee2( employee_id, manager_id, employee_first_name )
  2*   values( 3, 2, 'Emp2' )
SQL> /

1 row created.

那么當我們刪除經理時，員工的manager_id自動設置為NULL

SQL> delete from employee2
  2   where employee_first_name = 'Emp1';

1 row deleted.

SQL> select *
  2    from employee2
  3   where employee_first_name = 'Emp2';

EMPLOYEE_ID MANAGER_ID EMPLOYEE_FIRST_NAME
----------- ---------- ------------------------------
          3            Emp2