Question

我写了一个查询，它给了我一个数据列表，我需要选择前5个数据。例如

Num  Name
5    a
4    b
4    c
2    d
1    e
1    f
1    g
0    h

但是，如果我只使用LIMIT 5，则会遗漏名称为f和g的数据点。我怎么能从a-h中选择。这只是一个示例数据。我的实际数据包含更多行，所以我可以简单地排除底行。编辑对不起，当我说前5名我意味着前5名参赛作品。所以5,4,2,1,0但1有重复，所以我想选择所有这些重复

Answer 1

您可以通过在SQL逻辑中添加带有增量行号的新字段来计算，如下所示：

Feeds  Num  Name
  1     5    a
  2     4    b
  2     4    c
  3     2    d
  4     1    e
  4     1    f
  4     1    g
  5     0    h

然后将结果限制为所需的等级（在您的情况下为5）。以下是SQL供您参考：

SELECT num, name from (
SELECT @row_number:=CASE WHEN @num=num 
THEN @row_number ELSE @row_number+1 END AS feeds,@num:=num AS num, name
FROM table1, (SELECT @row_number:=0,@num:='') AS t
ORDER BY num desc 
  )t1
  WHERE feeds <= 5

SQL-fiddle link

Answer 2

我认为您需要这样的查询：

SELECT *
FROM (
    SELECT t1.Num, t1.Name, COUNT(DISTINCT t2.Num) AS seq
    FROM yourTable t1
        LEFT JOIN
        yourTable t2
        ON t1.Num <= t2.Num
    GROUP BY t1.Num, t1.Name) dt
WHERE (seq <= 5);

[SQL Fiddle Demo]

Answer 3

检查此查询

SELECT 
t1.Num, 
t1.Name,
FIND_IN_SET(t1.Num, SUBSTRING_INDEX(
       GROUP_CONCAT(DISTINCT(t2.Num ) ORDER BY t2.Num DESC), ',', 5)
) AS Ord
FROM yourTable t1
LEFT JOIN yourTable t2 ON(t2.Num IS NOT NULL)
GROUP BY t1.Name
ORDER BY t1.Num ASC

选择具有重复项的列中的前5位

3 个答案: