无法删除具有多个外键的数据

Question

这些是我的桌子：

CREATE TABLE COACH (
  COACH_ID  VARCHAR(8),
  COACH_NAME    VARCHAR(50),
  COACH_ADD VARCHAR(100),
  COACH_PHONENO CHAR(12),
  PRIMARY KEY (COACH_ID));

CREATE TABLE TEAM (
  TEAM_ID       VARCHAR(8),
  COACH_ID  VARCHAR(8),
  TEAM_NAME VARCHAR(50),
  TEAM_COLOUR   VARCHAR(10),
  PRIMARY KEY (TEAM_ID),
  CONSTRAINT TEAM_COACH_ID_FK 
  FOREIGN KEY (COACH_ID) REFERENCES COACH);

CREATE TABLE PARTICIPANT (
  PART_ID       VARCHAR(8),
  TEAM_ID       VARCHAR(8),
  SPORT_NAME    VARCHAR(15),
  PART_NAME VARCHAR(50),
  PART_IC       VARCHAR(14),
  PART_PHONENO  CHAR(12),
  PRIMARY KEY (PART_ID),
  CONSTRAINT SPORT_TEAM_ID_FK
  FOREIGN KEY (SPORT_NAME) REFERENCES SPORT,
  CONSTRAINT TEAM_TEAM_ID_FK
  FOREIGN KEY (TEAM_ID) REFERENCES TEAM );

这是我的 SQL：

DELETE FROM TEAM 
WHERE TEAM_COLOUR='Magenta';

代码产生了这个错误：

错误报告：
SQL 错误：ORA-02292：违反完整性约束 (HR.TEAM_TEAM_ID_FK) - 找到子记录
02292. 00000 - “违反完整性约束 (%s.%s) - 找到子记录”
*原因：试图删除具有外部依赖关系的父键值。 *操作：先删除依赖项，然后删除父项或禁用约束。

我想DELETE TEAM_COLOUR = 'MAGENTA'

Answer 1

首先删除所有 Team_Colour='Magenta' 团队成员的所有参与者。

然后你就可以删除团队了。

Answer 2

可能是这样的：

语法有效：但仍然不确定这是否适合您...

但请注意；级联删除可能很危险。如果你不小心删除了一个团队，你也会丢失所有的参与者信息......这就是为什么很多人喜欢做两个删除语句的原因。

ALTER TABLE PARTICIPANT
  DROP CONSTRAINT TEAM_TEAM_ID_FK;

ALTER TABLE PARTICIPANT
  ADD CONSTRAINT TEAM_TEAM_ID_FK
  FOREIGN KEY (TEAM_ID) 
  REFERENCES TEAM(TEAM_ID) 
  ON DELETE CASCADE;

然后

DELETE FROM TEAM WHERE TEAM_COLOUR='Magenta';

应该可以。

这是整个脚本：

CREATE TABLE COACH (
  COACH_ID  VARCHAR(8),
  COACH_NAME    VARCHAR(50),
  COACH_ADD VARCHAR(100),
  COACH_PHONENO CHAR(12),
  PRIMARY KEY (COACH_ID));

CREATE TABLE TEAM (
  TEAM_ID       VARCHAR(8),
  COACH_ID  VARCHAR(8),
  TEAM_NAME VARCHAR(50),
  TEAM_COLOUR   VARCHAR(10),
  PRIMARY KEY (TEAM_ID),
  CONSTRAINT TEAM_COACH_ID_FK 
  FOREIGN KEY (COACH_ID) REFERENCES COACH);

CREATE TABLE PARTICIPANT (
  PART_ID       VARCHAR(8),
  TEAM_ID       VARCHAR(8),
  SPORT_NAME    VARCHAR(15),
  PART_NAME VARCHAR(50),
  PART_IC       VARCHAR(14),
  PART_PHONENO  CHAR(12),
  PRIMARY KEY (PART_ID),
  CONSTRAINT TEAM_TEAM_ID_FK
  FOREIGN KEY (TEAM_ID) REFERENCES TEAM );

  insert into coach values (1,'Test1',NULL,NULL);
  Insert into Team values (1,1,'Test1','Blue');
  insert into team values (2,1,'Test1','Magenta');
  Insert into Participant (part_ID, Team_ID) values (1,1);
  Insert into Participant (part_ID, Team_ID) values (2,1);
  Insert into Participant (part_ID, Team_ID) values (3,2);

ALTER TABLE PARTICIPANT DROP Constraint TEAM_TEAM_ID_FK;

ALTER TABLE PARTICIPANT
  ADD CONSTRAINT TEAM_TEAM_ID_FK
  FOREIGN KEY (TEAM_ID) 
  REFERENCES TEAM(TEAM_ID) 
  ON DELETE CASCADE;
  DELETE FROM TEAM WHERE TEAM_COLOUR='Magenta';