单项选择题
The EMPLOYEES table has these columns:
LAST NAME VARCHAR2(35)
SALARY NUMBER(8,2)
HIRE_DATE DATE
Management wants to add a default value to the SALARY column. You plan to alter the table by using this SQL statement:
ALTER TABLE EMPLOYEES
MODIFY ( 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.
相关考题
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单项选择题
Examine the data in the EMPLOYEES table. On the EMPLOYEES table, EMPLOYEE_ID is the primary key. MGR_ID is the ID of managers and refers to the EMPLOYEE_ID. The JOB_ID column is a NOT NULL column. Evaluate this DELETE statement: Why does the DELETE statement fail when you execute it?（）
A. There is no row with dept_id 90 in the EMPLOYEES table.
B. You cannot delete the JOB_ID column because it is a NOT NULL column.
C. You cannot specify column names in the DELETE clause of the DELETE statement.
D. You cannot delete the EMPLOYEE_ID column because it is the primary key of the table. -
单项选择题
Which substitution variable would you use if you want to reuse the variable without prompting the user each time?（）
A.&
B.ACCEPT
C.PROMPT
D.&& -
单项选择题
What is true about the WITH GRANT OPTION clause?（）
A.It allows a grantee DBA privileges.
B.It is required syntax for object privileges.
C.It allows privileges on specified columns of tables.
D.It is used to grant an object privilege on a foreign key column.
E.It allows the grantee to grant object privileges to other users and roles.
