1Z0-007单项选择题每日一练(2020.04.25)

A. DELETE FROM employees WHERE employee_id = (SELECT employee_id FROM employees);
B. DELETE * FROM employees WHERE employee_id = (SELECT employee_id FROM new_ employees);
C. DELETE FROM employees WHERE employee_id IN (SELECT employee_id FROM new_employees WHERE name = ('Carrey')'
D. DELETE * FROM employees WHERE employee_id IN (SELECT employee_id FROM new_employees WHERE last_ name = ('Carrey')'

A. ALTER TABLE students ADD PRIMARY KEY student_id;
B. ALTER TABLE students ADD CONSTRAINT PRIMARY KEY (student _ id);
C. ALTER TABLE students ADD CONSTRAINT stud _ id _pk PRIMARY KEY (student _ id);
D. ALTER TABLE students MODIFY CONSTRAINT stud _ id _pk PRIMARY KEY (student _ id);

A. creates a view with constraints
B. creates a view even if the underlying parent table has constraints
C. creates a view in another schema even if you don't have privileges
D. creates a view regardless of whether or not the base tables exist

A. Substitution variables
B. Replacement variables
C. Prompt variables
D. Instead-of variables
E. This feature cannot be implemented through /SQL*Plus

A.SELECT ADD_MONTHS(MAX(hire_Date), 6) FROM EMP;
B.SELECT ROUND(hire_date) FROM EMP;
C.SELECT sysdate-hire_date FROM EMP;
D.SELECT TO_NUMBER(hire_date + 7) FROM EMP;