DBI202Xuất hiện trong 1 đề thi
Suppose relation R(A, B) has the following tuples: | A | B | |---|---| | 1 | a | | 2 | b | | 3 | a | | 4 | d | | 5 | e | | 6 | a | | 7 | g | The SQL statement to count distinct rows from column B in relation R is:
Các lựa chọn
ASELECT COUNT DISTINCT B AS 'Total_rows' FROM R;
BSELECT (COUNT DISTINCT B) AS 'Total_rows' from R;
CSELECT DISTINCT B AS 'Total_rows' from R;
DSELECT COUNT (DISTINCT(B)) AS 'total_rows' FROM R;