| DROP TABLE D |
| DROP TABLE C |
| DROP TABLE B |
| DROP TABLE A |
| go |
| |
| CREATE TABLE A |
| ( |
| ID INT PRIMARY KEY, |
| NAME VARCHAR(32) NULL |
| ) |
| |
| CREATE TABLE B |
| ( |
| ID INT PRIMARY KEY, |
| NAME VARCHAR(32) NULL, |
| AID INT NULL, |
| FOREIGN KEY (AID) REFERENCES A (ID) |
| ) |
| |
| CREATE TABLE C |
| ( |
| ID INT PRIMARY KEY, |
| NAME VARCHAR(32) NULL, |
| AID INT NULL, |
| BID INT NULL, |
| FOREIGN KEY (AID) REFERENCES A (ID), |
| FOREIGN KEY (BID) REFERENCES B (ID) |
| ) |
| |
| CREATE TABLE D |
| ( |
| ID INT PRIMARY KEY, |
| NAME VARCHAR(32) NULL, |
| AID INT NULL, |
| BID INT NULL, |
| CID INT NULL, |
| FOREIGN KEY (AID) REFERENCES A (ID), |
| FOREIGN KEY (BID) REFERENCES B (ID), |
| FOREIGN KEY (CID) REFERENCES C (ID) |
| ) |
| |
| go |
| |