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单选题
If a unique constraint is defined on column COL1 of table TAB1, what are the characteristics of COL1?()
A

COL1 will accept NULL values and can be referenced in another table's foreign key specification.

B

COL1 will not accept NULL values and cannot be referenced in another tables foreign key specification.

C

COL1 will not accept NULL values and can be referenced in another tables foreign key specification.

D

COL1 will accept NULL values and cannot be referenced in another tables foreign key specification.


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更多 “单选题If a unique constraint is defined on column COL1 of table TAB1, what are the characteristics of COL1?()A COL1 will accept NULL values and can be referenced in another table's foreign key specification.B COL1 will not accept NULL values and cannot be referenced in another tables foreign key specification.C COL1 will not accept NULL values and can be referenced in another tables foreign key specification.D COL1 will accept NULL values and cannot be referenced in another tables foreign key specification.” 相关考题
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考题 单选题Which of the following scenarios will ensure that the value of the NEXT_STEPNO column in a given row of table TABLEX exists as a value of column STEPNO (usually in another row) in the same table?()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.

考题 单选题Given the following DDL and INSERT statements: CREATE VIEW v1 AS SELECT col1 FROM t1 WHERE col1 10; CREATE VIEW v2 AS SELECT col1 FROM v1 WITH CASCADED CHECK OPTION; CREATE VIEW v3 AS SELECT col1 FROM v2 WHERE col1 100; INSERT INTO v1 VALUES(5); INSERT INTO v2 VALUES(5); INSERT INTO v3 VALUES(20); INSERT INTO v3 VALUES(100); How many of these INSERT statements will be successful?()A 0B 1C 2D 3

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考题 多选题Which two statements are true about constraints? ()AThe UNIQUE constraint does not permit a null value for the column.BA UNIQUE index gets created for columns with PRIMARY KEY and UNIQUE constraints.CThe PRIMARY KEY and FOREIGN KEY constraints create a UNIQUE index.DThe NOT NULL constraint ensures that null values are not permitted for the column.

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考题 单选题Given the following requirements: Create a table to contain employee data, with a unique numeric 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')) );

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考题 单选题Given the following requirements:Create a table named TESTTAB, which has an identity column named ACTIVITYNO. Define the identity column to generate the values for the column by default. Start the values at 10 and increment by 10. Make the identity column unique. Which of the following CREATE statements will successfully create this table?()A CREATE TABLE TESTTAB (ACTIVITYNO SMALLINT NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 10 INCREMENT BY 10), ACTKWD CHAR(6) NOT NULL, ACTDESC VARCHAR(20) NOT NULL, UNIQUE(ACTIVITYNO))B CREATE TABLE TESTTAB (ACTIVITYNO SMALLINT NOT NULL GENERATED ALWAYS AS IDENTITY (START WITH 1 INCREMENT BY 10), ACTKWD CHAR(6) NOT NULL, ACTDESC VARCHAR(20) NOT NULL, UNIQUE(ACTNO))C CREATE TABLE TESTTAB (ACTIVITYNO SMALLINT NOT NULL GENERATED BY DEFAULT AS IDENTITY (START WITH 10 INCREMENT BY 1), ACTKWD CHAR(6) NOT NULL, ACTDESC VARCHAR(20) NOT NULL, UNIQUE(ACTIVITYNO))D CREATE TABLE TESTTAB (ACTIVITYNO SMALLINT NOT NULL GENERATED BY DEFAULT AS IDENTITY (START WITH 10 INCREMENT BY 10), ACTKWD CHAR(6) NOT NULL, ACTDESC VARCHAR(20) NOT NULL, UNIQUE(ACTIVITYNO))

考题 单选题When defining a referential constraint between the parent table T2 and the dependent table T1, which of the following is true?()A The list of column names in the FOREIGN KEY clause can be a subset of the list of column names in the primary key of T2 or a UNIQUE constraint that exists on T2.B The list of column names in the FOREIGN KEY clause can be a subset of the list of column names in the primary key of T1 or a UNIQUE constraint that exists on T1.C The list of column names in the FOREIGN KEY clause must be identical to the list of column names in the primary key of T2 or a UNIQUE constraint that exists on T2.D The list of column names in the FOREIGN KEY clause must be identical to the list of column names in the primary key of T1 or a UNIQUE constraint that exists on T1.