A.SELECT * FROM student where id=l,2,3:
B.SELECT * FROM student where (id=1, id=2, id=3)
C.SELECT * FROM student where id in (1,2,3)
D.SELECT * FROM student where id in 1,2,3
A.投影、选择运算
B.选择、投影运算
C.并、交运算
D.交、并运算
A.SELECT单位,COUNT(借阅.借书证号)FROM借阅,读者WHERE借阅.借书证号=读者.借书证号ORDERBY单位
B.SELECT单位,COUNT(借阅.借书证号)FROM借阅,读者WHERE借阅.借书证号=读者.借书证号GROUPBY单位
C.SELECT单位,SUM(借阅.借书证号)FROM借阅,读者WHERE借阅.借书证号=读者.借书证号HAVING单位
D.SELECT单位,SUM(借阅.借书证号)FROM借阅,读者WHERE借阅.借书证号=读者.借书证号GROUPBY单位