题目内容（请给出正确答案）

[主观题]

The manager of the company firmly believed that one of the important______sources of new c

ustomers was the children's market.

A．unfolded

B．unknown

C．unsolved

D．untapped

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更多“The manager of the company fir…”相关的问题

第1题

Which constraint can be defines only at the column level？（）

A．UNIQUE

B． NOT NULL

C． CHECK

D． PRIMARY KEY

E． FOREIGN KEY

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第2题

Which SQL statement defines the FOREIGN KEY constraint on the DEPTNO column of the EMP table？（）

A. CREATE TABLE EMP (empno NUMBER(4), ename VARCNAR2(35), deptno NUMBER(7,2) NOT NULL CONSTRAINT emp_deptno_fk FOREIGN KEY deptno REFERENCES dept deptno);

B. CREATE TABLE EMP (empno NUMBER(4), ename VARCNAR2(35), deptno NUMBER(7,2) CONSTRAINT emp_deptno_fk REFERENCES dept (deptno));

C. CREATE TABLE EMP (empno NUMBER(4) ename VARCHAR2(35), deptno NUMBER(7,2) NOT NULL, CONSTRAINT emp_deptno_fk REFERENCES dept (deptno) FOREIGN KEY (deptno));

D. CREATE TABLE EMP (empno NUMBER(4), ename VARCNAR2(35), deptno NUMBER(7,2) FOREIGN KEY CONSTRAINT emp deptno fk REFERENCES dept (deptno));

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第3题

在 SQL 中，（)约束的关键字为 primary key ，外码约束的关键字为 foreign key。

在 SQL 中，()约束的关键字为 primary key ，外码约束的关键字为 foreign key。

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第4题

Which statement explicitly names a constraint？（）

A. ALTER TABLE student_grades ADD FOREIGN KEY (student_id) REFERENCES students (student_id);

B. ALTER TABLE student_grades ADD CONSTRAINT NAME = student_id_fk FOREIGN KEY (student_id) REFERENCES students (student_id);

C. ALTER TABLE student_grades ADD CONSTRAINT student_id_fk FOREIGN KEY (student_id) REFERENCES students (student_id);

D. ALTER TABLE student grades ADD NAMED CONSTRAINT student_id_fk FOREIGN KEY (student_id) REFERENCES students (student_id);

E. ALTER TABLE student grades ADD NAME student_id_fk FOREIGN KEY (student_id) REFERENCES students (student_id);

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第5题

在SQL中，primary key为约束的关键字，foreign key为 __________约束的关键字。

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第6题

A．

B．

C．

D．

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第7题

Which of the following will be a consequence of defining the column IDCOL2 in TABLE2 as a foreign key referencing the primary key （IDCOL1) of TABLE1？（）

A.DB2 will no longer allow updating the value of IDCOL1 in TABLE1.

B.When inserting a row in TABLE2, the only values that DB2 will allow for IDCOL2 are the existing values of IDCOL1.

C.When inserting a row in TABLE2, DB2 will only allow foreign values for IDCOL2, that is values which do not exist in IDCOL1.

D.When a SELECT statement joins TABLE1 with TABLE2, DB2 will automatically add the condition TABLE1.IDCOL1=TABLE2.IDCOL2 if not specified in the statement.

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