我有一个包含大量重复数据的电子邮件列表，我想合并在某一列中具有重复数据的行。
这是我的表：
autoid,title,lastname,firstname,middlename,prefix,
fulladdress,address1,address2,
city,state,zip,country,county,phone1,phone2,email,id, ts
我想根据 email 和 phone1 合并重复的行。如果这些内容在两行中相同，那么我想合并这些行并填写任何空白，然后删除第二行。具有较低 autoid 的行中的数据将优先于具有较高 id 的行。
如果我们可以使用单个 mysql 查询来做到这一点，那就太好了，但如果我们必须使用 PHP，那也可以。
您可以使用类似的东西将多行组合成一个单行
GROUP BY email, phone1
如果你只是插入这个，你会得到任何一个组合行。如果您希望值优先于NULL字段，则可以使用聚合函数，例如MIN：
SELECT MIN(title), MIN(lastname), …
FROM tableName
GROUP BY email, phone1
但这会决定为每一行分别取哪个值。组合行但以您描述的方式进行的查询在 MySQL 中会相当棘手。您可以有一个查询，它按匹配列的顺序列出所有行，然后降序排列autoid，使用用户变量来填补空白。但是不填补不匹配行中的空白会很困难，因此每个匹配对的一个子查询可能会更好。除了查询的性能和可读性之外，总的来说，使用 PHP 解决方案可能会更好。
在 PHP 中，事情应该相当简单：查询数据库
ORDER BY email, phnone1, autoid ASC
然后在 PHP 端，对于您从数据库中读取的每一行，检查它是否与两个特定列中先前读取的行匹配。如果是这样，请遍历列，随时替换nulls 。这些天我不是一个 PHP 编码器，所以其他人可能更适合为此编写代码片段。
我们真的不喜欢在 StackOverflow 上提供完整的代码解决方案，通常我们会帮助您编写自己的代码解决方案，但我不确定我是否可以在没有实际编写代码自己弄清楚的情况下解释所有步骤，所以在这里是一些入门代码。
这是未经测试的原始代码
首先复制您现有的表格，直到我们知道此代码不会损害或删除您现有的数据，然后在副本上执行所有操作，然后在解决它并且您已经验证它可以正常工作然后将其应用到正确的桌子。
使用以下命令创建副本：
CREATE TABLE EmailListCopy LIKE EmailList;
INSERT EmailListCopy SELECT * FROM EmailList;
PHP代码：
<?php
//This script will first query the table for ALL results, store them in arrays,
//then loop through the arrays to search the table for duplicates using individual
//sql queries and then compare the results, update the entry as needed and delete the
//duplicate row. THIS CODE IS NOT OPTIMIZED!! DO NOT RUN CONTINUOUSLY!! This should be
//used for OCCASIONAL merging ONLY!! i.e. Once-a-day or once-a-week etc...
$result="";
$duplicatesFound;
//Setup arrays to hold the original query information
$autoidArray = array();
$titleArray = array();
$lastnameArray = array();
$firstnameArray = array();
$middlenameArray = array();
$prefixArray = array();
$fulladdressArray = array();
$address1Array = array();
$address2Array = array();
$cityArray = array();
$stateArray = array();
$zipArray = array();
$countryArray = array();
$countyArray = array();
$phone1Array = array();
$phone2Array = array();
$emailArray = array();
$idArray = array();
$tsArray = array();
$link=mysqli_connect($hostname,$dbname,$password,$username);
if(mysqli_connect_errno())
{
$result="Error connecting to database: ".mysqli_connect_error();
}
else
{
$stmt=mysqli_prepare($link,"SELECT autoid,title,lastname,firstname,middlename,prefix,fulladdress,address1,address2,city,state,zip,country,county,phone1,phone2,email,id,ts FROM " . $table);
mysqli_stmt_execute($stmt);
mysqli_stmt_bind_result($stmt, $autoid, $title, $lastname, $firstname, $middlename, $prefix, $fulladdress, $address1, $address2, $city, $state, $zip, $country, $county, $phone1, $phone2, $email, $id, $ts);
if(mysqli_stmt_errno($stmt))
{
$result="Error executing SQL statement: ".mysqli_stmt_error($stmt);
}
else
{
mysqli_stmt_store_result($stmt);
if(mysqli_stmt_num_rows($stmt)==0)
{
$result="0 rows returned (Empty table)";
}
else
{
while(mysqli_stmt_fetch($stmt))
{
//Load results into arrays
array_push($autoidArray, $autoid);
array_push($titleArray, $title);
array_push($lastnameArray, $lastname);
array_push($firstnameArray, $firstname);
array_push($middlenameArray, $middlename);
array_push($prefixArray, $prefix);
array_push($fulladdressArray, $fulladdress);
array_push($address1Array, $address1);
array_push($address2Array, $address2);
array_push($cityArray, $city);
array_push($stateArray, $state);
array_push($zipArray, $zip);
array_push($countryArray, $country);
array_push($countyArray, $county);
array_push($phone1Array, $phone1);
array_push($phone2Array, $phone2);
array_push($emailArray, $email);
array_push($idArray, $id);
array_push($tsArray, $ts);
}
}
mysqli_stmt_free_result($stmt);
}
for($i=0;$i<count($emailArray);$i++)
{
$duplicatestmt=mysqli_prepare($link,"SELECT autoid,title,lastname,firstname,middlename,prefix,fulladdress,address1,address2,city,state,zip,country,county,phone1,phone2,email,id,ts FROM " . $table . " WHERE email=? OR phone1=?");
mysqli_stmt_bind_param($duplicatestmt, 'si', $emailArray[$i], $phone1Array[$i]);
mysqli_stmt_execute($duplicatestmt);
mysqli_stmt_bind_result($duplicatestmt, $autoid, $title, $lastname, $firstname, $middlename, $prefix, $fulladdress, $address1, $address2, $city, $state, $zip, $country, $county, $phone1, $phone2, $email, $id, $ts);
if(mysqli_stmt_errno($duplicatestmt))
{
$result="Error executing SQL statement: ".mysqli_stmt_error($duplicatestmt);
}
else
{
mysqli_stmt_store_result($duplicatestmt);
if(mysqli_stmt_num_rows($duplicatestmt)==0)
{
//NO Duplicate entry found, loop again;
echo "<p>No Dublicate Found</p>";
}
else
{
while(mysqli_stmt_fetch($duplicatestmt))
{
//Found a duplicate
echo "<p>Dublicate Found</p>";
if($autoid > $autoidArray[$i])
{
if($email=="" && $phone1=="")
{
echo "<p>Both email and phone1 are empty. Skipping...</p>";
else
{
$duplicatesFound++;
//The autoid of the duplicate just found is greater then the autoid of the
//one used to find the duplicate (older). Therefor update the entry and remove the
//duplicate
//
//This checks each of the values and if the lower autoid one is blank, then will add the
//value to the table in the lower autoid row
//NOTE:** If having any problems with the queries below try removing the single quotes -> ' <- from any "autoid=" portion of the query
if($titleArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$title."' WHERE autoid='".$autoidArray[$i]."'");}
if($lastnameArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$firstname."' WHERE autoid='".$autoidArray[$i]."'");}
if($firstnameArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$lastname."' WHERE autoid='".$autoidArray[$i]."'");}
if($middlenameArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$middlename."' WHERE autoid='".$autoidArray[$i]."'");}
if($prefixArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$prefix."' WHERE autoid='".$autoidArray[$i]."'");}
if($fulladdressArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$fulladdress."' WHERE autoid='".$autoidArray[$i]."'");}
if($address1Array[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$address1."' WHERE autoid='".$autoidArray[$i]."'");}
if($address2Array[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$address2."' WHERE autoid='".$autoidArray[$i]."'");}
if($cityArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$city."' WHERE autoid='".$autoidArray[$i]."'");}
if($stateArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$state."' WHERE autoid='".$autoidArray[$i]."'");}
if($zipArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$zip."' WHERE autoid='".$autoidArray[$i]."'");}
if($countryArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$country."' WHERE autoid='".$autoidArray[$i]."'");}
if($countyArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$county."' WHERE autoid='".$autoidArray[$i]."'");}
if($phone1Array[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$phone1."' WHERE autoid='".$autoidArray[$i]."'");}
if($phone2Array[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$phone2."' WHERE autoid='".$autoidArray[$i]."'");}
if($emailArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$email."' WHERE autoid='".$autoidArray[$i]."'");}
if($idArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$id."' WHERE autoid='".$autoidArray[$i]."'");}
if($tsArray[$i]==""){mysqli_query($link,"UPDATE EmailListCopy SET title='".$ts."' WHERE autoid='".$autoidArray[$i]."'");}
//Now that it has been updated, delete the duplicate entry
mysqli_query($link, "DELETE FROM EmailListCopy WHERE autoid='".$autoid."'");
echo "<p>Duplicate to be updated DELETE FROM EmailListCopy WHERE autoid='".$autoid."'</p>";
}
}
else
{
//The duplicate autoid is lower then the one used to query either an entry we already but is still in the arrays, or something else.
//This is to be skipped.
echo "<p>Duplicate not to be updated</p>";
}
}
$result="Merged ".$duplicatesFound." rows.";
}
mysqli_stmt_free_result($stmt);
}
}
mysqli_stmt_close($duplicatestmt);
mysqli_stmt_close($stmt);
mysqli_close($link);
}
echo $result;
?>