Question

我有一个如下的MySQL查询；我想在具有180万条记录的表中为600条记录的每个范围选择最高记录。到目前为止，我必须循环3,000次才能完成此操作，但这不是有效的解决方案。

数据库架构；

 Table: bet_perm_13predict
 id     bet_id      perm_id     avg_odd     avg_odd2    avg_odd3
 1      23          1           43.29       28.82       28.82
 2      23          2           42.86       28.59       28.59
 3      23          3           43.13       28.73       28.73


 Table: bet_permute_13games
 perm_id    perm_code
 1      0000000000000
 2      0000000000001
 3      0000000000002
 4      0000000000010

用PHP示例MySQL查询

$totRange   = 0; //Used as starting point in rang
$range      = 600; //Used as range
$stop       = 0;//Used as endPoint of range

while($totRange < 1800000){
    $stop   = $totRange+$range;

    $sql = "SELECT (tb1.avg_odd2 + tb1.avg_odd3) AS totAvg_odd ,
    tb1.perm_id , tb1.avg_odd, tb1.avg_odd2, tb1.avg_odd3, tb2.perm_code 
    FROM bet_perm_13predict tb1 
    INNER JOIN bet_permute_13games tb2 ON tb2.perm_id = tb1.perm_id
    WHERE tb1.bet_id = '$bet_id' && tb1.perm_id 
    BETWEEN $startRange AND $stop ORDER BY totAvg_odd ASC LIMIT 1"

    $q1    = $this->db->query($sql);
    $totRange = $stop;
}

换句话说，我想选择一个表示整个表的数据样本，该样本不是随机的，而是使用600范围内的最高记录预定义的。到目前为止，我不知道如何进行。没有关于此主题的清晰在线材料。

Answer 1

您可以使用整数除法创建组。

DEMO

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然后找到每个组的最大值。一些选项

Get records with max value for each group of grouped SQL results

Answer 2

对于那些可能遇到相同问题的人，这就是我解决的方法。我使用@Juan Carlos建议，并添加了一种使用Subquery来选择组的最高记录的方法。

SELECT * FROM 
         (SELECT * , perm_id DIV $limit as grp , (avg_odd2 + avg_odd3) AS totAvg_odd 
           FROM bet_perm_13predict WHERE bet_id = '$bet_id'  ORDER BY grp ASC ) tb1
INNER JOIN bet_permute_13games tb2 ON tb2.perm_id = tb1.perm_id
INNER JOIN bet_entry tb3 ON tb3.bet_id = tb1.bet_id
WHERE tb1.avg_odd2 < (SELECT AVG(avg_odd2) FROM bet_perm_13predict WHERE bet_id = '$bet_id' )
                     && tb1.avg_odd3 < (SELECT AVG(avg_odd3) FROM bet_perm_13predict WHERE bet_id = '$bet_id' )
GROUP BY grp ORDER BY totAvg_odd ASC
LIMIT 100

从数百万行的MySQL查询中选择第N条记录

2 个答案: