Given table T1 has column I1 co

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.A table referenced in the FROM clause has no indexed column.

B.The table referenced in the FROM clause has more than 200 columns.

C.Two or more tables in the FROM clause have identical column names.

D.The FROM clause contains two or more tables in the SELECT statement.

The EMPLOYEES table has these columns:LAST NAME VARCHAR2(35)SALARY NUMBER(8,2)HIRE_DATE DATEManagement wants to add a default value to the SALARY column. You plan to alter the table by using this SQL statement:ALTER TABLE EMPLOYEESMODIFY ( SALARY DEFAULT 5000);What is true about your ALTER statement?（）

A. Column definitions cannot be altered to add DEFAULT values.

B. A change to the DEFAULT value affects only subsequent insertions to the table.

C. Column definitions cannot be altered at add DEFAULT values for columns with a NUMBER data type.

D. All the rows that have a NULL value for the SALARY column will be updated with the value 5000.

利用SQL命令删除“学生”表中的“年龄”字段，正确的命令格式是（ ）。

A)ALTER TABLE 学生 DELETE COLUMN 年龄

B)ALTER TABLE 学生 DROP COLUMN 年龄

C)ALTER TABLE 学生 CANCEL COLUMN 年龄

D)ALTER TABLE 学生 CUT COLUMN 年龄

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))

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.

A.Define the column MAINID as NOT UPDATABLE

B.Define the column MAINID as a PRIMARY KEY

C.Define the column MAINID as a FOREIGN KEY

D.Define an UPDATE trigger on table TABLEX

A. Column definitions cannot be altered to add DEFAULT values.

B. A change to the DEFAULT value affects only subsequent insertions to the table.

C. Column definitions cannot be altered at add DEFAULT values for columns with a NUMBER data type.

D. All the rows that have a NULL value for the SALARY column will be updated with the value 5000.

A.Check

B.Range

C.Referential

D.Informational