未知题型
有两个关系R和T如下：
.jpg)
则由关系R得到关系T的操作是
- A.shangxueba.cn/images/ct_ctvbbz20103_ctvbbchoosef_00010(20104).jpg'
B.选择
B．投影
C．交
D．并
【参考答案】
A
解析：关系T中的两行和关系R中的最后两行一致，通过选择运算即可由R得到T。
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