DBI202Xuất hiện trong 1 đề thi
Suppose that tuple $t$ appears, respectively, $x$, $y$, and $z$ times in the relations $X$, $Y$, and $Z$. Let $t$ appear $w$ times in the relation: $X \cup (Y \cap Z)$ Which of the following inequalities is true?
Các lựa chọn
A$w \le x+y$
B$w \le y+z$
C$w \ge z$
D$w \le \max(x,y)$