OCP认证051考试题库：11g-v9.02-第169题
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169. View the Exhibit and examine the description for the PRODUCTS and SALES table.
PROD_ID is a primary key in the PRODUCTS table and foreign key in the SALES table. You want to
remove all the rows from the PRODUCTS table for which no sale was done for the last three years.
Which is the valid DELETE statement?
A. DELETE
FROM products
WHERE prod_id = (SELECT prod_id
FROM sales
WHERE time_id - 3*365 = SYSDATE );
B. DELETE
FROM products
WHERE prod_id = (SELECT prod_id
FROM sales
WHERE SYSDATE >= time_id - 3*365 );
C. DELETE
FROM products
WHERE prod_id IN (SELECT prod_id
FROM sales
WHERE SYSDATE - 3*365 >= time_id);
D. DELETE
FROM products
WHERE prod_id IN (SELECT prod_id
FROM sales
WHERE time_id >= SYSDATE - 3*365 );
Answer: C
试题解析：
题意要求：从PRODUCTS表移除所有过去三年没有销售过的产品行
SYSDATE - 3*365 <= time_id三年前之前的时间，三年前多，
SYSDATE - 3*365 >= time_id三年前之后的时间，三年前往后面数，即应该用这个
即选C
