有一片均匀生长的草地，可供27头羊吃2天，或供23头羊吃3天，那么它可供21头羊吃几天？()

A.Automatic

B.Dynamic

C.Reuse

D.Manual

A.Define a UNIQUE constraint on the columns NEXT_STEPNO and STEPNO.

B.Define a CHECK constraint on the NEXT_STEPNO column (NEXT_STEPNO = STEPNO).

C.Define column STEPNO as the primary key of TABLEX and column NEXT_STEPNO as a foreign key referencing column STEPNO of the same table.

D.Define column NEXT_STEPNO as the primary key of TABLEX and column STEPNO as a foreign key referencing column NEXT_STEPNO in the same table.

A.TS3310

B.TS3500

C.TS3400

D.TS3200

A.GRAPHIC

B.BINARY

C.IMAGE

D.BLOB

A.theminimumis1andthemaximumis8

B.theminimumis2andthemaximumis8

C.theminimumis2andthemaximumis16

D.theminimumis1andthemaximumis64

A.存储分区功能

B.弹性的扩展能力

C.增强了地址范围、逻辑卷池、光纤交换磁盘通道灵活应对客户商业需求

D.以上所有

meric identifier automatically assigned when a row is added, has an EDLEVEL column that permits only the values ‘C‘, ‘H‘ and ‘N‘, and permits inserts only when a corresponding value for the employee‘s department exists in the DEPARTMENT table.Which of the following CREATE statements will successfully create this table?（）

A.CREATE TABLE emp ( empno SMALLINT NEXTVAL GENERATED ALWAYS AS IDENTITY, firstname VARCHAR(30) NOT NULL, lastname VARCHAR(30) NOT NULL, workdept CHAR(3) NOT NULL, edlevel CHAR(1), PRIMARY KEY emp_pk (empno), FOREIGN KEY emp_workdept_fk ON (workdept) REFERENCES department (deptno), CHECK edlevel_ck VALUES (edlevel IN (‘C‘,‘H‘,‘N‘)), );

B.CREATE TABLE emp ( empno SMALLINT NOT NULL GENERATED BY DEFAULT AS IDENTITY, firstname VARCHAR(30) NOT NULL, lastname VARCHAR(30) NOT NULL, workdept CHAR(3), edlevel CHAR(1), CONSTRAINT emp_pk PRIMARY KEY (empno), CONSTRAINT emp_workdept_fk FOREIGN KEY (workdept) REFERENCES department (deptno), CONSTRAINT edlevel_ck CHECK edlevel VALUES (‘C‘,‘H‘,‘N‘) );

C.CREATE TABLE emp ( empno SMALLINT NEXTVAL GENERATED BY DEFAULT AS IDENTITY, firstname VARCHAR(30) NOT NULL, lastname VARCHAR(30) NOT NULL, workdept CHAR(3) NOT NULL, edlevel CHAR(1) CHECK IN (‘C‘,‘H‘,‘N‘)), CONSTRAINT emp_pk PRIMARY KEY (empno), CONSTRAINT emp_workdept_fk FOREIGN KEY department (deptno) REFERENCES (workdept) );

D.CREATE TABLE emp ( empno SMALLINT NOT NULL GENERATED BY DEFAULT AS IDENTITY, firstname VARCHAR(30) NOT NULL, lastname VARCHAR(30) NOT NULL, workdept CHAR(3), edlevel CHAR(1), CONSTRAINT emp_pk PRIMARY KEY (empno), CONSTRAINT emp_workdept_fk FOREIGN KEY (workdept) REFERENCES department (deptno), CONSTRAINT edlevel_ck CHECK (edlevel IN (‘C‘,‘H‘,‘N‘)) );

A.init 0

B.telinit m

C.shutdown -FM

D.sh /etc/rc.maint

A.2001

B.2B00

C.3A01

D.5E00

A.view

B.strings

C./usr/sbin/viwtmp

D./usr/sbin/acct/fwtmp