A subquery can be used to 的考题!
Q: 17 A subquery can be used to ___.
A. create groups of data
B. sort data in a specific order
C. convert data to a different format
D. retrieve data based on an unknown condition
Answer: D
这道题答案为什么是D,子查询是可以管理表查询出另外一个数据吧。