一、原表:
courseid coursename score
-------------------------------------
1 java 70
2 oracle 90
3 xml 40
4 jsp 30
5 servlet 80
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为了便于阅读,查询此表后的结果显式如下(及格分数为60):
courseid coursename score mark
---------------------------------------------------
1 java 70 pass
2 oracle 90 pass
3 xml 40 fail
4 jsp 30 fail
5 servlet 80 pass
---------------------------------------------------
写出此查询语句

select courseid, coursename ,score ,decode（sign(score-60),-1,'fail','pass') as mark from course

如果score>60,sign(score-60)=1;

score==60,sign(score-60)=0;

score<60,sign(score-60)=-1;