有什么方法可以创建此触发器还是我应该使用其他东西？

Question

这些是表格：

CREATE TABLE Staff 
(
     staffID INTEGER,
     staffName VARCHAR(20),
     staffSurname VARCHAR(20),
     DOB DATE NOT NULL,
     staffBranchNo INTEGER,
     salary DECIMAL(5,2),
     startDateOfWork DATE
);

ALTER TABLE Staff
ADD (CONSTRAINT staff_pk PRIMARY KEY(staffID));

CREATE TABLE Branch 
(
     branchNo INTEGER,
     branchCity varchar(20),
     branchTotalStaffNumber INTEGER
);

ALTER TABLE Branch
ADD (CONSTRAINT branch_pk PRIMARY KEY(branchNo));

我需要一个触发器，根据 staffBranchNo 更新 branchTotalStaffNumber，当添加新员工时，更新或删除现有员工。

我尝试了一些触发器，但 none 其中包括我需要的三个操作。下面的触发器不起作用。

CREATE OR REPLACE TRIGGER staff_trigger
BEFORE INSERT OR UPDATE OR DELETE ON Staff
FOR EACH ROW
BEGIN

  CASE
    WHEN INSERTING THEN
    INSERT INTO branch (branchTotalStaffNumber) 
    VALUES(:NEW.branchTotalStaffNumber);
         
    WHEN UPDATING THEN
    UPDATE branch SET branchTotalStaffNumber = :NEW.branchTotalStaffNumber;
    
    WHEN DELETING THEN
    delete from branch where staffBranchNo = :new.branchTotalStaffNumber;
    
  END CASE;
END;
/

Answer 1

您不应使用 trigger 来存储计算值。但是如果你正在学习那么你应该使用下面的代码（见内联评论）

CREATE OR REPLACE TRIGGER staff_trigger
  BEFORE INSERT OR UPDATE OR DELETE ON Staff
  FOR EACH ROW
  BEGIN
      IF INSERTING THEN -- used IF . CASE usage is not allowed as IF
        UPDATE branch SET branchTotalStaffNumber = branchTotalStaffNumber + 1
    Where branchno = :new.staffBranchNo; -- used :new to identify the record
    
      ELSIF UPDATING THEN 
        -- update the branch table only if staffBranchno is updated
        -- adding one staff to the new branch
        IF :new.staffBranchNo <> :old.staffBranchNo THEN
          UPDATE branch SET branchTotalStaffNumber = branchTotalStaffNumber + 1
    Where branchno = :new.staffBranchNo;
          -- removing one staff from old branch
          UPDATE branch SET branchTotalStaffNumber = branchTotalStaffNumber - 1
    Where branchno = :old.staffBranchNo;
        END IF;
      ELSE -- IF DELETING can be omitted
        -- removing one staff from branch for delete action 
        UPDATE branch SET branchTotalStaffNumber = branchTotalStaffNumber - 1
    Where branchno = :old.staffBranchNo;
        
      END IF;
END;
/

请注意，您还可以使用 OF 子句和其中的列名来创建触发器。仅当 OF 子句中提到的列的值更改时才会执行触发器。

有什么方法可以创建此触发器还是我应该使用其他东西？

Is there any way to create this trigger or should I use something else?

sql

oracle

oracle-sqldeveloper