以下是PATIENT、PHYSICIAN和ADMISSION表的结果：
PATIENT
|
| PATIENT_ID | NUMBER | NOT NULL, Primary Key |
| LAST_NAME | VARCHAR2(30) | NOT NULL |
| FIRST_NAME | VARCHAR2(25) | NOT NULL |
| DOB | DATE | |
| INS_CODE | NUMBER | |
PHYSICIAN
|
| PHYSICIAN_ID | NUMBER | NOT NULL, Primary Key |
| LAST_NAME | VARCHAR2(30) | NOT NULL |
| FIRST_NAME | VARCHAR2(25) | NOT NULL |
| LICENSE_NO | NUMBER(7) | NOT NULL |
| HIRE_DATE | DATE | |
ADHISSION
|
| PATIENT_ID | NUMBER | NOT NULL, Primary Key, References PATIENT_ID column of
the PATIENT table |
|
| PHYSICIAN_ID | NUMBER | NOT NULL, Primary Key, References PHYSICIAN_ID column
of the PHYSICIAN table |
|
| ADMIT_DATE | DATE | |
| DISCHG_DATE | DATE | |
| ROOH_ID | NUHBER | Foreign key to ROOM_ID of the ROOM table |
如果想提取在某个理疗师(physician)被雇佣之后所有注册的病人(patient)，应使用如下的哪种结构
A．一个分组函数
B．一个HAVING子句
C．一个MERGE语句
D．一个单行子查询