多项选择题
A. DELETE employees; B. DESCRIBE employees; C. ROLLBACK TO SAVE POINT C; D. GRANT SELECT ON employees TO SCOTH E. ALTER TABLE employees SET UNUSED COLUMN sal; F. Select MAX(sal) FROM employees WHERE department _ id 20;
The DBA issues this SQL command: CREATE USER scott IDEN...
单项选择题
The DBA issues this SQL command: CREATE USER scott IDENTIFIES by tiger; What privileges does the user Scott have at this point?（）
A. No privileges. B. Only the SELECT privilege. C. Only the CONNECT privilege. D. All the privileges of a default user.
The EMPLOYEES table has these columns: LAST NAME VARCHA...
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.
Examine the data in the EMPLOYEES table. On the EMPLOY...
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.
