在 SQL 中拥有子类的外键的正确方法？
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【中文标题】在 SQL 中拥有子类的外键的正确方法？【英文标题】：Proper way to have foreign keys to subclasses in SQL? 【发布时间】：2018-05-19 19:43:35 【问题描述】：一名护士通过对三种不同用品之一的申请订购医疗用品，所有用品均由供应商提供。
护士>申请
由于项目可以是三种类型之一，并且可能尚不存在项目的申请，因此申请表具有 3 种供应类型的外键。
问题：我正确列出的外键都指向 3 个不同的表，除了其中一个之外，每个表都没有对应的外键。
我收到以下错误：
第 1 行出现错误：ORA-02091：事务回滚 ORA-02291: 违反完整性约束 (MMM1339.ITEMNO_PHAR_FK) - 未找到父键
CREATE TABLE SUPPLIER
(SUPPLIERNO INT,
SUPPLIERNAME VARCHAR2(100),
PHONENO VARCHAR2(12),
ADDRESS VARCHAR(100),
FAXNO VARCHAR(12),
CONSTRAINT SUPPLIERNO_SSPL_PK PRIMARY KEY(SUPPLIERNO));
CREATE TABLE SUPPLIES_PHARMACEUTICAL
(ITEMNO INT,
SUPPLIERNO INT,
NAME VARCHAR2(25),
DESCRIPTION VARCHAR2(25),
QUANTITYINSTOCK INT,
REORDERLEVEL INT,
COSTPERUNIT DECIMAL(6,2),
DOSAGE VARCHAR2(12),
CONSTRAINT ITEMNO_PHAR_PK PRIMARY KEY(ITEMNO));
CREATE TABLE SUPPLIES_SURGICAL
(ITEMNO INT,
NAME VARCHAR2(25),
DESCRIPTION VARCHAR2(25),
QUANTITYINSTOCK INT,
REORDERLEVEL INT,
COSTPERUNIT DECIMAL(6,2),
SUPPLIERNO INT,
CONSTRAINT ITEMNO_SUP_PK PRIMARY KEY(ITEMNO));
CREATE TABLE SUPPLIES_NONSURGICAL
(ITEMNO INT,
NAME VARCHAR2(25),
DESCRIPTION VARCHAR2(25),
QUANTITYINSTOCK INT,
REORDERLEVEL INT,
COSTPERUNIT DECIMAL(6,2),
SUPPLIERNO INT,
CONSTRAINT ITEMNO_NONSURG_PK PRIMARY KEY(ITEMNO));
CREATE TABLE STAFF_CHARGENURSE
(STAFFNO INT,
ADDRESS VARCHAR2(25),
POSITION VARCHAR2(12),
BUDGET DECIMAL(6,2),
SPECIALTY VARCHAR2(12),
CONSTRAINT STAFFNO_CHNURSE_PK PRIMARY KEY(STAFFNO));
CREATE TABLE REQUISITION
(REQNO INT,
STAFFNO INT,
STAFFNAME VARCHAR2(25),
WARDNO INT,
ITEMNO INT,
QUANTITY INT,
DATEORDERED DATE,
DATERECIEVED DATE,
CONSTRAINT REQ_PK PRIMARY KEY(REQNO));
外键：
ALTER TABLE SUPPLIES_PHARMACEUTICAL
ADD CONSTRAINT SUPPLIERNO_PHA_FK FOREIGN KEY(SUPPLIERNO) REFERENCES SUPPLIER(SUPPLIERNO)
DEFERRABLE INITIALLY DEFERRED;
ALTER TABLE SUPPLIES_SURGICAL
ADD CONSTRAINT SUPPLIERNO_SURG_FK FOREIGN KEY(SUPPLIERNO) REFERENCES SUPPLIER(SUPPLIERNO)
DEFERRABLE INITIALLY DEFERRED;
ALTER TABLE SUPPLIES_NONSURGICAL
ADD CONSTRAINT SUPPLIERNO_NONSURG_FK FOREIGN KEY(SUPPLIERNO) REFERENCES SUPPLIER(SUPPLIERNO)
DEFERRABLE INITIALLY DEFERRED;
ALTER TABLE REQUISITION
ADD CONSTRAINT STAFFNO_REQ_FK FOREIGN KEY(STAFFNO) REFERENCES STAFF_CHARGENURSE(STAFFNO)
DEFERRABLE INITIALLY DEFERRED;
ALTER TABLE REQUISITION
ADD CONSTRAINT ITEMNO_PHAR_FK FOREIGN KEY(ITEMNO) REFERENCES SUPPLIES_PHARMACEUTICAL(ITEMNO)
DEFERRABLE INITIALLY DEFERRED;
ALTER TABLE REQUISITION
ADD CONSTRAINT ITEMNO_SURG_FK FOREIGN KEY(ITEMNO) REFERENCES SUPPLIES_SURGICAL(ITEMNO)
DEFERRABLE INITIALLY DEFERRED;
ALTER TABLE REQUISITION
ADD CONSTRAINT ITEMNO_NONSURG_FK FOREIGN KEY(ITEMNO) REFERENCES SUPPLIES_NONSURGICAL(ITEMNO)
DEFERRABLE INITIALLY DEFERRED;
测试数据：
INSERT INTO REQUISITION VALUES(1, 20, 'Julie Wood', 8, 888520, 2, '27-FEB-2018', '15-MAR-2018');
INSERT INTO REQUISITION VALUES(2, 20, 'Julie Wood', 8, 923956, 1, '25-FEB-2018', '28-FEB-2018');
INSERT INTO REQUISITION VALUES(3, 21, 'Sarah Michaels', 7, 054802, 3, '20-FEB-2018', '22-FEB-2018');
INSERT INTO SUPPLIES_PHARMACEUTICAL VALUES (823456, 100001, 'Zanax', 'Anti Depressant', 8, 2, 100.50, '50mg');
INSERT INTO SUPPLIES_PHARMACEUTICAL VALUES (923956, 100001, 'Zupridol', 'Blood Pressure Treatment', 12, 5, 50, '20mg');
INSERT INTO SUPPLIES_PHARMACEUTICAL VALUES (3952, 200001, 'Amibreezax', 'Artificial Ear Wax', 2, 1, 200, '5g');
INSERT INTO SUPPLIES_PHARMACEUTICAL VALUES (4955, 200001, 'Ambridax', 'Skin Treatment', 5, 10, 20, '2mg');
INSERT INTO SUPPLIES_SURGICAL VALUES (54802, 'Scalpel', 'Surgical Tool', 20, 10, 200.42, 100001);
INSERT INTO SUPPLIES_SURGICAL VALUES (634520, 'Stitches', 'Suture Tool', 100, 10, 2.50, 200001);
INSERT INTO SUPPLIES_NONSURGICAL VALUES (888520, 'Cart', '5ftx2ftx3ft', 2, 0, 200.00, 100001);
INSERT INTO SUPPLIES_NONSURGICAL VALUES (423, 'Tool Holder', 'Holds Inspection Equip.', 4, 2, 50.00, 100001);
INSERT INTO STAFF_CHARGENURSE VALUES(20, '32 Stark St. Portland, OR', 'Charge Nurse', 8000.99, 'Head Trauma');
INSERT INTO STAFF_CHARGENURSE VALUES(21, '18 Wilson Rd Portland, OR', 'Charge Nurse', 6000, 'Epidermus');
INSERT INTO SUPPLIER VALUES (100001,'Company A', '503-222-3333', '100 SE Stark Rd Portland, OR', '503-666-4444');
INSERT INTO SUPPLIER VALUES (200001,'Company B', '666-333-4444', '500 SE Bilerica Rd Akron, OH', '666-444-3333');
COMMIT;
【问题讨论】：
如果这是您尝试运行的脚本，唯一的问题是您的插入顺序是错误的，首先您是 suplies_whatever，然后是供应商，然后是员工，最后是您的申请表，即链接表全部。要获得链接，链接的项目必须首先存在。 已重新排序，但仍然存在同样的问题。 【参考方案1】：正如您在其他相关问题的回复中所述，没有超类和子类。 SUPPLIES_PHARMACEUTICAL、SUPPLIES_SURGICAL 和 SUPPLIES_NONSURGICAL 只是表，彼此没有联系。
所有启用的约束都被强制执行。将它们定义为可延迟只是将验证推迟到下一个commit，这并没有真正改变您的示例中的任何内容。如果您在列上定义三个约束，则没有语法或机制可以说“只需要强制执行这些约束中的一个”，我看不出这样的系统将如何工作.
在数据建模中，您可以使用任一定义子类型
-
带有
category 或类似指示列的单个表（例如SUPPLIES），或
父表仅具有公共列，其下的子表仅具有特定于类型的列，通过外键约束链接回父表。子表可以在 FK 列上具有唯一键或主键，使其成为可选的 1:1 关系。
然后，其他表可以根据需要具有引用父级或其子级之一的 FK 约束。
【讨论】：
【参考方案2】：这是您修改后的原始代码（大写原始，小写：修改），使用 @William Robertson 的 ideas：1 使用单个 SUPPLIES 表，2 使用 is_surgical 列，3 使用 pharma_dosage桌子。也许你喜欢它...
CREATE TABLE SUPPLIER
(SUPPLIERNO integer,
SUPPLIERNAME VARCHAR2(100),
PHONENO VARCHAR2(12),
ADDRESS VARCHAR(100),
FAXNO VARCHAR(12),
CONSTRAINT SUPPLIERNO_SSPL_PK PRIMARY KEY(SUPPLIERNO));
-- one table instead of 3
create table supplies (
ITEMNO integer,
SUPPLIERNO integer,
NAME VARCHAR2(25),
DESCRIPTION VARCHAR2(25),
QUANTITYINSTOCK integer,
REORDERLEVEL integer,
COSTPERUNIT number(6,2),
is_surgical varchar2(1) not null,
constraint supplies_surgical_yn_chk check( is_surgical in ('Y','N') )
, constraint supplies_pk primary key( itemno )
, constraint supplies_fk foreign key( supplierno )
references supplier( supplierno )
);
create table pharma_dosage (
itemno integer
, dosage varchar2( 64 ) not null
, constraint pharma_supplies_fk foreign key( itemno )
references supplies( itemno )
, constraint pharma_supplies_pk primary key( itemno )
);
另外两个表，并且 - 注释掉 - 我们不需要的东西：
-- not needed
-- CREATE TABLE SUPPLIES_PHARMACEUTICAL
-- CREATE TABLE SUPPLIES_SURGICAL
-- CREATE TABLE SUPPLIES_NONSURGICAL
CREATE TABLE STAFF_CHARGENURSE
(STAFFNO integer,
ADDRESS VARCHAR2(25),
POSITION VARCHAR2(12),
BUDGET DECIMAL(6,2),
SPECIALTY VARCHAR2(12),
CONSTRAINT STAFFNO_CHNURSE_PK PRIMARY KEY(STAFFNO));
CREATE TABLE REQUISITION
(REQNO integer,
STAFFNO integer,
STAFFNAME VARCHAR2(25),
WARDNO integer,
ITEMNO integer,
QUANTITY integer,
DATEORDERED DATE,
DATERECIEVED DATE,
CONSTRAINT REQ_PK PRIMARY KEY(REQNO),
constraint req_fk foreign key ( itemno ) references supplies ( itemno )
);
-- not needed
-- ALTER TABLE SUPPLIES_PHARMACEUTICAL ADD CONSTRAINT SUPPLIERNO_PHA_FK
-- ALTER TABLE SUPPLIES_SURGICAL ADD CONSTRAINT SUPPLIERNO_SURG_FK
-- ALTER TABLE SUPPLIES_NONSURGICAL ADD CONSTRAINT SUPPLIERNO_NONSURG_FK
ALTER TABLE REQUISITION ADD CONSTRAINT STAFFNO_REQ_FK
FOREIGN KEY(STAFFNO) REFERENCES STAFF_CHARGENURSE(STAFFNO) DEFERRABLE INITIALLY DEFERRED;
-- not needed
-- ALTER TABLE REQUISITION ADD CONSTRAINT ITEMNO_PHAR_FK
-- ALTER TABLE REQUISITION ADD CONSTRAINT ITEMNO_SURG_FK
-- ALTER TABLE REQUISITION ADD CONSTRAINT ITEMNO_NONSURG_FK
插入
-- parents first
begin
INSERT INTO STAFF_CHARGENURSE VALUES(20, '32 Stark St. Portland, OR', 'Charge Nurse', 8000.99, 'Head Trauma');
INSERT INTO STAFF_CHARGENURSE VALUES(21, '18 Wilson Rd Portland, OR', 'Charge Nurse', 6000, 'Epidermus');
INSERT INTO SUPPLIER VALUES (100001,'Company A', '503-222-3333', '100 SE Stark Rd Portland, OR', '503-666-4444');
INSERT INTO SUPPLIER VALUES (200001,'Company B', '666-333-4444', '500 SE Bilerica Rd Akron, OH', '666-444-3333');
end;
/
PL/SQL procedure successfully completed.
更多测试数据
begin
-- pharmaceutical
INSERT INTO SUPPLIES( itemno, supplierno, name, description, quantityinstock
, reorderlevel, costperunit, is_surgical )
VALUES (823456, 100001, 'Zanax', 'Anti Depressant', 8, 2, 100.50, 'N');
INSERT INTO SUPPLIES( itemno, supplierno, name, description, quantityinstock
, reorderlevel, costperunit, is_surgical )
VALUES (923956, 100001, 'Zupridol', 'Blood Pressure Treatment', 12, 5, 50, 'N');
INSERT INTO SUPPLIES( itemno, supplierno, name, description, quantityinstock
, reorderlevel, costperunit, is_surgical )
VALUES (3952, 200001, 'Amibreezax', 'Artificial Ear Wax', 2, 1, 200, 'N');
INSERT INTO SUPPLIES( itemno, supplierno, name, description, quantityinstock
, reorderlevel, costperunit, is_surgical )
VALUES (4955, 200001, 'Ambridax', 'Skin Treatment', 5, 10, 20, 'N');
-- pharma_dosage
insert into pharma_dosage ( itemno, dosage ) values ( 823456, '50mg' ) ;
insert into pharma_dosage ( itemno, dosage ) values ( 923956, '20mg' ) ;
insert into pharma_dosage ( itemno, dosage ) values ( 3952, '5g' ) ;
insert into pharma_dosage ( itemno, dosage ) values ( 4955, '2mg' ) ;
-- surgical
INSERT INTO SUPPLIES( itemno, supplierno, name, description, quantityinstock
, reorderlevel, costperunit, is_surgical )
VALUES (54802, 100001, 'Scalpel', 'Surgical Tool', 20, 10, 200.42, 'Y');
INSERT INTO SUPPLIES( itemno, supplierno, name, description, quantityinstock
, reorderlevel, costperunit, is_surgical )
VALUES (634520, 200001, 'Stitches', 'Suture Tool', 100, 10, 2.50, 'Y');
-- nonsurgical
INSERT INTO SUPPLIES( itemno, supplierno, name, description, quantityinstock
, reorderlevel, costperunit, is_surgical)
VALUES (888520, 100001, 'Cart', '5ftx2ftx3ft', 2, 0, 200.00, 'N');
INSERT INTO SUPPLIES( itemno, supplierno, name, description, quantityinstock
, reorderlevel, costperunit, is_surgical )
VALUES (423, 100001,'Tool Holder', 'Holds Inspection Equip.', 4, 2, 50.00, 'N');
-- requisition
INSERT INTO REQUISITION VALUES(1, 20, 'Julie Wood', 8, 888520, 2, '27-FEB-2018', '15-MAR-2018');
INSERT INTO REQUISITION VALUES(2, 20, 'Julie Wood', 8, 923956, 1, '25-FEB-2018', '28-FEB-2018');
INSERT INTO REQUISITION VALUES(3, 21, 'Sarah Michaels', 7, 054802, 3, '20-FEB-2018', '22-FEB-2018');
end ;
/
PL/SQL procedure successfully completed.
现在，一些 SELECT ...
SQL> select * from supplier ;
SUPPLIERNO SUPPLIERNAME PHONENO ADDRESS FAXNO
100001 Company A 503-222-3333 100 SE Stark Rd Portland, OR 503-666-4444
200001 Company B 666-333-4444 500 SE Bilerica Rd Akron, OH 666-444-3333
SQL> select * from supplies ;
ITEMNO SUPPLIERNO NAME DESCRIPTION QUANTITYINSTOCK REORDERLEVEL COSTPERUNIT IS_SURGICAL
823456 100001 Zanax Anti Depressant 8 2 100.5 N
923956 100001 Zupridol Blood Pressure Treatment 12 5 50 N
3952 200001 Amibreezax Artificial Ear Wax 2 1 200 N
4955 200001 Ambridax Skin Treatment 5 10 20 N
54802 100001 Scalpel Surgical Tool 20 10 200.42 Y
634520 200001 Stitches Suture Tool 100 10 2.5 Y
888520 100001 Cart 5ftx2ftx3ft 2 0 200 N
423 100001 Tool Holder Holds Inspection Equip. 4 2 50 N
SQL> select * from requisition;
REQNO STAFFNO STAFFNAME WARDNO ITEMNO QUANTITY DATEORDERED DATERECIEVED
1 20 Julie Wood 8 888520 2 27-FEB-18 15-MAR-18
2 20 Julie Wood 8 923956 1 25-FEB-18 28-FEB-18
3 21 Sarah Michaels 7 54802 3 20-FEB-18 22-FEB-18
SQL> select * from staff_chargenurse;
STAFFNO ADDRESS POSITION BUDGET SPECIALTY
20 32 Stark St. Portland, OR Charge Nurse 8000.99 Head Trauma
21 18 Wilson Rd Portland, OR Charge Nurse 6000 Epidermus
SQL> select * from pharma_dosage;
ITEMNO DOSAGE
823456 50mg
923956 20mg
3952 5g
4955 2mg
第 2 版
如果您仍然想要一个“超类型”和 3 个“子类型”表，请查看以下 DDL。您可能会找到一种介于两者之间的解决方案。 （以下只是“概念证明”代码，省略了几列和一些原始表格。）
create table supplies (
supplierno number primary key
, category varchar2( 16 )
, constraint unique_parentcategory unique ( supplierno, category )
, constraint check_category check (
category in ( 'surgical', 'non-surgical', 'pharmaceutical' )
)
);
然后……
create table supplies_pharmaceutical (
supplierno number primary key
, category varchar2( 16 )
--
-- more "specific" columns here
--
, constraint check_category1 check ( category in ( 'pharmaceutical' ) )
, constraint s_p_fk foreign key ( supplierno, category )
references supplies ( supplierno, category )
) ;
create table supplies_nonsurgical (
supplierno number primary key
, category varchar2( 16 )
--
-- more "specific" columns here
--
, constraint check_category2 check ( category in ( 'non-surgical' ) )
, constraint s_n_fk foreign key ( supplierno, category )
references supplies ( supplierno, category )
) ;
create table supplies_surgical (
supplierno number primary key
, category varchar2( 16 )
--
-- more "specific" columns here
--
, constraint check_category3 check ( category in ( 'surgical' ) )
, constraint s_s_fk foreign key ( supplierno, category )
references supplies ( supplierno, category )
) ;
测试数据：
begin
insert into supplies( supplierno, category ) values ( 1000, 'pharmaceutical' ) ;
insert into supplies( supplierno, category ) values ( 2000, 'non-surgical' ) ;
insert into supplies( supplierno, category ) values ( 3000, 'surgical' ) ;
insert into supplies_pharmaceutical( supplierno, category )
values ( 1000, 'pharmaceutical' ) ;
insert into supplies_nonsurgical( supplierno, category )
values ( 2000, 'non-surgical' ) ;
insert into supplies_surgical( supplierno, category )
values ( 3000, 'surgical' ) ;
end;
/
-- must fail:
insert into supplies ( supplierno, category ) values ( 1001, 'food' ) ;
insert into supplies_pharmaceutical( supplierno, category )
values ( 2000, 'pharmaceutical' ) ;
【讨论】：
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