我需要根据同一amount的最小order number删除重复记录。表有100k记录，结构是这样的。
<{1}}在此表中为tmp_id。
primary key我尝试使用
将------------------------------------
user_id order_number amount tmp_id
-------------------------------------
15 12364 25 1
20 454544 75 2
4 12364 100 3
6 45487 45 4
8 454544 330 5
最少量的重复记录。{
delete当我执行此代码时，出现$qb_duplicate_data_query="select user_id,order_number,amount from tmp_qbappraiser limit 10";
$qb_duplicate_data_sql=mysql_query($qb_duplicate_data_query) or die(mysql_error());
while($row=mysql_fetch_array($qb_duplicate_data_sql)) {
$amount=$row['amount'];
$order_no=$row['order_number'];
$sql="SELECT c1.tmp_id from tmp_qbappraiser c1
inner join (SELECT tmp_id FROM tmp_qbappraiser WHERE order_number='$order_no' ORDER BY amount asc) AS c
on c.tmp_id=c1.tmp_id GROUP BY c1.order_number having count(order_number)>1";
$query=mysql_query($sql) or die(mysql_error());
$result=mysql_fetch_array($query);
$db_tmp_id=$result['tmp_id'];
if($db_tmp_id!='') {
$delete_sql="delete from tmp_qbappraiser where order_number='$order_no' and tmp_id='$db_tmp_id'";
$delete_query=mysql_query($delete_sql) or die(mysql_error());
}
}
错误。如何优化我的查询或有没有其他方法来删除数以千计的记录？
答案 0 :(得分：1)
您不需要编写多个查询来删除重复条目，这可以通过一个查询来完成。
delete t1 from tmp_qbappraiser t1
join tmp_qbappraiser t2
on t1.order_number = t2.order_number
and t1.amount < t2.amount ;
以上查询将保留每order_number的最大金额，并将删除其余的。
您可能需要在表格中添加一些索引才能加快速度
alter table tmp_qbappraiser add index ord_amt_idx(order_number,amount);
注意：确保在应用索引并运行删除查询之前备份表。