問題描述

我有以下代碼.mysqli_insert_id()(在本例中為$last_row")，它應該返回表的最后一行，總是返回 0.為什么會這樣?

I have the following code. The mysqli_insert_id() (in this case "$last_row"), which is supposed to return the last row of the table, is always returning 0. Why is it so?

<?php

include 'connect-db.php';
$last_row = mysqli_insert_id($connection);

if ($content != '') {
    $sql = "INSERT INTO myCity VALUES (NULL, 'Stuttgart', 'DEU', 'Stuttgart', 617000)";

    if (!mysqli_query($connection, $sql)) {
        die('Error: ' . mysqli_error($connection));
    }

    echo $last_row;
    mysqli_close($connection);
}

推薦答案

mysqli_insert_id 確實不返回表最后一行的 ID.從文檔，它:

mysqli_insert_id does not return the ID of the last row of the table. From the docs, it:

...返回對具有 AUTO_INCREMENT 屬性的列的表的查詢生成的 ID.如果最后一個查詢不是 INSERT 或 UPDATE 語句，或者如果修改后的表沒有具有 AUTO_INCREMENT 屬性的列，則此函數將返回零.

...returns the ID generated by a query on a table with a column having the AUTO_INCREMENT attribute. If the last query wasn't an INSERT or UPDATE statement or if the modified table does not have a column with the AUTO_INCREMENT attribute, this function will return zero.

(我的重點)

也就是說，如果您在自動生成 ID 的插入操作之后立即運行它，那么在您進行插入操作的同一個連接上，它將返回為該插入操作生成的 ID.

That is, if you were to run it immediately after an insert that auto-generated an ID, on the same connection you did the insert with, it would return the ID generated for that insert.

上面鏈接的文檔中的示例說明了這一點:

This is illustrated by the example in the docs linked above:

$query = "INSERT INTO myCity VALUES (NULL, 'Stuttgart', 'DEU', 'Stuttgart', 617000)";
$mysqli->query($query);

printf ("New Record has id %d.
", $mysqli->insert_id);

這篇關于為什么 mysqli_insert_id() 總是返回 0?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！