外鍵我有兩個表名爲EMPLOYEE和DEPARTMENT如下:關於一個表的主鍵作爲另一個表
CREATE table "EMPLOYEE" (
"EMP_ID" NUMBER,
"ENAME" VARCHAR2(4000),
"SALARY" VARCHAR2(4000),
"COMPANY" VARCHAR2(4000),
"CONTACTNO." NUMBER,
"GENDER" CHAR(100),
constraint "EMPLOYEE_PK" primary key ("EMP_ID")
)
CREATE TABLE "DEPARTMENT"
(
"DEPT_ID" NUMBER,
"DEPT_NAME" VARCHAR2(4000),
"LOCATION" VARCHAR2(4000),
"CONTACTNO." NUMBER,
CONSTRAINT "DEPARTMENT_PK" PRIMARY KEY ("DEPT_ID") ENABLE
)
現在我試圖讓EMPLOYEE表的EMP_ID作爲主鍵EMPLOYEE表本身,但它應該作爲DEPARTMENT表中的DEPT_ID的外鍵,請告知如何實現這一點!
大概這是一個化妝的例子吧?在EMPLOYEE中的EMP_ID列與DEPARTMENT中的DEPT_ID列之間存在外鍵關係是沒有意義的。如果你真的有這兩個表,你會想添加一個'DEPT_ID'列到'EMPLOYEE',它引用'DEPARTMENT'的'DEPT_ID'。假設這是一個虛構的例子,你是否希望'EMPLOYEE'成爲外鍵關係中的父表或子表? –
爲什麼你不應該在員工表中擁有department_id? – gks
@JustinCave Employee是父表,它應該引用爲DEPARTMENT表 –