16、（7-5） choose the best answer
The PRODUCTS table has the following structure:
Evaluate the following two SQL statements:
SQL>SELECT prod_id, NVL2(prod_expiry_date, prod_expiry_date + 15,'')
FROM products;
SQL>SELECT prod_id, NVL(prod_expiry_date, prod_expiry_date + 15)
FROM products;
Which statement is true regarding the outcome?
A) Both the statements execute and give different results.
B) Both the statements execute and give the same result.
C) Only the second SQL statement executes successfully.
D) Only the first SQL statement executes successfully.
Answer：A
（解析：NVL2 的意思是如果第一个表达式不为空，则返回第二表达式的值，否则返回第三表达式
SQL> select sal,comm,nvl2(comm,comm+10,0) from emp;
SAL COMM NVL2(COMM,COMM+10,0)
---------- ---------- --------------------
800 0
1600 300 310
1250 500 510
2975 0
）