10/17练习
0.1和0.2在进行加法之前从十进制变为二进制进行计算，0.1变为0.00011001100110011001100110011001100110011001100110011001，
0.2变为0.00110011001100110011001100110011001100110011001100110011，
相加之后的结果为0.01001100110011001100110011001100110011001100110011001100转化为十进制变为0.30000000000000004，不为0.3
2.
SELECT * FROM student_score WHERE name in(SELECT name FROM student_score WHERE name LIKE “张%” GROUP BY name HAVING AVG(score) >75);
3.