多项选择题
Which two statements complete a transaction? （）
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;
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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. -
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. -
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. &&
