007的一道題

显示全部楼层 · 2013-1-29 11:27:26

In which case would you use a FULL OUTER JOIN?
A. Both tables have NULL values.
B. You want all unmatched data from one table.
C. You want all matched data from both tables.
D. You want all unmatched data from both tables.
E. One of the tables has more data than the other.
F. You want all matched and unmatched data from only one table.
答案應該選什么﹖是不是選A合理點﹖

千问 · 2013-1-29 11:27:26

ding

千问 · 2013-1-29 11:27:26

是不是选d呀

千问 · 2013-1-29 11:27:26

选择d，因为要把两个表中不匹配的值都显示出来

千问 · 2013-1-29 11:27:26

是嘛﹐D的意思是說只將unmatched的資料顯示出來。而全連接應該是將matched和unmatched的數據都應該顯示出來呀。

千问 · 2013-1-29 11:27:26

应该是D，Both tables have NULL values 并不一定要用FULL OUTER JOIN。

千问 · 2013-1-29 11:27:26

Both tables have NULL values 不用FULL OUTER JOIN﹐還可以用什么其它方法﹖

千问 · 2013-1-29 11:27:26

不懂期待答案，，