[英]update a column so duplicated values becomes unique
列title
有很多重复值,不止一次。
我需要更新该列,例如,如果'gold'
重复 - 它变为'gold 1'
、 'gold 2'
等。
像这样的东西:
$st = $db->query("select id, title from arts order by title asc");
$st->execute();
$x = 0;
while($row = $st->fetch()){
$title = $row['title'];
//if($title.is duplicated){
$x++;
$title .= ' ' . $x;
$stb = $db->query("update arts set title = '" . $title . "' where id = " . $row['id']);
$stb->execute();
}
}
有什么帮助吗?
在纯 SQL 中执行此操作会比使用 PHP 更有效。 这是一种使用窗口函数的方法,可在 MySQL 8.0 中使用。
您可以使用子查询来计算每条记录存在多少title
重复,并为具有相同title
的记录组中的每条记录分配一个等级。 然后,您可以将子查询与要更新的表进行JOIN
。 如果存在多个记录,您可以将行号附加到组中的每条记录。
询问:
UPDATE arts a
INNER JOIN (
SELECT
id,
title,
COUNT(*) OVER(PARTITION BY title) cnt,
ROW_NUMBER() OVER(PARTITION BY title ORDER BY id) rn
FROM arts
) b ON a.id = b.id
SET a.title = CONCAT(a.title, b.rn)
WHERE cnt > 1;
样本数据:
| id | title |
| --- | ------ |
| 10 | silver |
| 20 | gold |
| 30 | gold |
| 40 | bronze |
| 50 | gold |
| 60 | bronze |
运行更新查询后的结果:
| id | title |
| --- | ------- |
| 10 | silver |
| 20 | gold1 |
| 30 | gold2 |
| 40 | bronze1 |
| 50 | gold3 |
| 60 | bronze2 |
请参阅下面对我有用的代码
// Create connection
$conn = new mysqli($servername, $username, $password,$dbname);
// get all row
$sql = "select id, title from arts order by title asc";
$result = $conn->query($sql);
while ($row=$result->fetch_assoc()) {
$title=$row['title'];
// select where title is same
$sql = "select * from arts where title='".$title."'";
$result2 = $conn->query($sql);
// if number of row is greater then one
if ($result2->num_rows > 1){
$x=0;
while ($row2=$result2->fetch_assoc()) {
$id=$row2['id'];
// skip first row
if($x>0){
$newTitle=$title.' '.$x;
$uquery = "update arts set title='".$newTitle."' where title='".$title."' and id=$id";
$update = $conn->query($uquery);
}
$x++;
}
}
}
并在查询运行后
这适用于 MySql 5.7:
update arts a inner join (
select * from (
select t.id,
(
select count(*) + 1 from arts
where id < t.id and title = t.title
) counter
from arts t
) t
) t on t.id = a.id
set a.title = concat(a.title, ' ', t.counter)
where a.title in (
select h.title from (
select title from arts
group by title
having count(*) > 1
) h
);
请参阅演示。
对于数据:
| id | title |
| --- | -------- |
| 1 | silver |
| 2 | gold |
| 3 | diamond |
| 4 | bronze |
| 5 | gold |
| 6 | bronze |
| 7 | gold |
结果是
| id | title |
| --- | -------- |
| 1 | silver |
| 2 | gold 1 |
| 3 | diamond |
| 4 | bronze 1 |
| 5 | gold 2 |
| 6 | bronze 2 |
| 7 | gold 3 |
我认为在 SQL 中执行此操作会更有效,但是您可以执行一个函数来验证重复项,如下所示:
function isDuplicated( $title, $db ){
$dp = $db->query("SELECT * FROM arts WHERE title = $title");
if ( $dp->num_rows > 1)
return true;
return false;
}
$st = $db->query("select id, title from arts order by title asc");
$st->execute();
$x = 0;
while($row = $st->fetch()){
$title = $row['title'];
if( isDuplicated( $title, $db ) ){
$x++;
$title .= ' ' . $x;
$stb = $db->query("update arts set title = '" . $title . "' where id = " . $row['id']);
$stb->execute();
}
}
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