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现有表stu(id,name,sex,class)和索引 idx_key1(name,class),下列可以使用覆盖索引的查询包括:
A、select count(name) from stu;
B、select name,class from stu where name='pw';
C、select name,class,sex from stu where name='pw' and class='class-05-12';
D、select * from stu where class='class-05-12';