Question

我尝试了两种方法但在mysql中失败了。

/*see top 50% students, but this sql can't work*/
select * from student_table order by chinese_score desc limit count(*) * 0.5 ;

/*also can't work*/
set @num= floor((select count(*) from test.student_score)*0.5);
select * from student_table order by chinese_score desc limit @num ;

如何在mysql中解决？

Answer 1

在 Mysql 中，可以使用user defined variables在单个查询中完成此操作。

您可以在一个语句中将值存储在用户定义的变量中稍后在另一个声明中提及它。这使您可以通过从一个陈述到另一个陈述的价值。

SELECT * FROM    (
          SELECT student_table.*, @counter := @counter +1 AS counter
          FROM (SELECT @counter:=0) AS initvar, student_table
          ORDER BY student_table.chinese_score DESC
        ) AS result
WHERE counter < (@counter/2) ORDER BY chinese_score DESC;

SQL限制结果达到50％

1 个答案: