php 如何使用 MySQL 获取最后一行值？
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How can I get the last row value with MySQL?
提问by John Doe
I have a table called Live, and in the table I have public_id. In public_idare numbers (e.g. 1,2,3,4,5). How can I get the highest number or the last entry's number?
我有一张桌子叫Live，在桌子上我有public_id。输入的public_id是数字（例如 1,2,3,4,5）。如何获得最高数字或最后一个条目的数字？
回答by santiagobasulto
I'd choose
我会选择
SELECT public_id FROM Live ORDER BY public_id DESC LIMIT 1;
It has already been posted, but i'll add something more:
它已经发布了，但我会添加更多内容：
If you perform this query usually you can create an index with inverted ordering.
如果您通常执行此查询，您可以创建一个反向排序的索引。
Something like:
就像是：
CREATE INDEX ON Live (public_id DESC)
Please Note
请注意
DESC
发展研究中心
PHP + MySQL code:
PHP + MySQL 代码：
<?php
$result = mysql_query('SELECT public_id FROM Live ORDER BY public_id DESC LIMIT 1;');
if (mysql_num_rows($result) > 0) {
$max_public_id = mysql_fetch_row($result);
echo $max_public_id[0]; //Here it is
}
?>
回答by Mobius
SELECT public_id FROM Live ORDER BY public_id DESC LIMIT 1;
would give you the highest number
会给你最高的数字
Edit: For the php
编辑：对于 php
$conn = mysql_connect(....
$query = "SELECT public_id FROM Live ORDER BY public_id DESC LIMIT 1";
$result = mysql_query($query, $conn);
回答by ain
Another option is to use MAX, ie
另一种选择是使用MAX，即
SELECT MAX(public_id) FROM Live
回答by ludesign
You can either use ORDER BY public_id DESC LIMIT 1;to obtain the record with the highest id (I guess you are using autoincrement attribute on public_id) or MySQL MAX()function like this:
您可以使用ORDER BY public_id DESC LIMIT 1;获取具有最高 id 的记录（我猜您在 public_id 上使用 autoincrement 属性）或这样的MySQL MAX()函数：
SELECT * FROM table WHERE public_id = MAX(public_id);
edit:
编辑：
Here is how you will do it in php:
以下是您将如何在 php 中执行此操作：
// executing the QUERY request to MySQL server, mysql_query() returns resource ID
$result = mysql_query('SELECT public_id FROM Live ORDER BY public_id DESC LIMIT 1');
// then we use this resource ID to fetch the actual value MySQL have returned
$row = mysql_fetch_array($result, MYSQL_FETCH_ASSOC);
// $row variable now holds all the data we got from MySQL, its an array, so we just output the public_id column value to the screen
echo $row['public_id']; // you can use var_dump($row); to see the whole content of $row
