SQL錯誤：ORA-02270：沒有匹配的唯一或主鍵此列列表

Question

加入一些外鍵約束到2臺輸出，監事時，我有一個問題：

ALTER TABLE OUTPUT ADD CONSTRAINT PROJECT_OUTPUT_FK 
FOREIGN KEY (proj_id) 
REFERENCES PROJECT (proj_id) 
NOT DEFERRABLE; 

ALTER TABLE SUPERVISOR ADD CONSTRAINT PROJECT_SUPERVISOR_FK 
FOREIGN KEY (proj_id) 
REFERENCES PROJECT (proj_id) 
NOT DEFERRABLE; 

錯誤顯示：

SQL Error: ORA-02270: no matching unique or primary key for this column-list 

02270. 00000 - "no matching unique or primary key for this column-list" 
*Cause: A REFERENCES clause in a CREATE/ALTER TABLE statement 
      gives a column-list for which there is no matching unique or primary 
      key constraint in the referenced table. 
*Action: Find the correct column names using the ALL_CONS_COLUMNS 
      catalog view 

在這種情況下該怎麼辦？

Answer 1

確保您在表PROJECT的PROJ_ID列上定義了主鍵或唯一鍵。您可以使用此查詢這個（如果適當替換用戶/所有者），並找出哪些列的PK/UK的一部分：

select c.owner, c.constraint_name, c.constraint_type, cc.column_name 
    from all_constraints c 
    join all_cons_columns cc on cc.owner = c.owner and cc.constraint_name = c.constraint_name 
where c.constraint_type in ('P', 'U') 
    and c.table_name = 'PROJECT' 
     and c.owner = user 
order by cc.position; 

如果需要還創建一個主鍵，你有需要的權限，你可以這樣做：

ALTER TABLE PROJECT ADD CONSTRAINT PK_PROJECT PRIMARY KEY (proj_id); 

Answer 2

謝謝你們我想我想通了。由於PROJECT表中的主鍵是組合鍵，因此屬性的數量與SUPERVISOR和OUTPUT中的屬性不匹配，因此會彈出錯誤消息。