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金虎4年前
1、 isset() :判断变量是否定义,是否存在; empty():判断变量的值是否为空。 2、
function mysort($arr){ for($i=0;$i
select * from student order by class asc,score desc; select class,sum(if(score>=60,1,0)) jige,sum(if(score < 60,1,0) bujige from student group by class;
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