PHP MySQL检查重复条目吗? [英] PHP MySQL Check for duplicate entry?

问题描述

如何检查数据库中是否已经有重复的条目?我不想阻止它，只是警告.因此，如果它已经存在，它只会发出警告，这取决于用户是否忽略它.
预先感谢！

How can I check if there already is a duplicate entry in the database? I don't want to prevent it, just a warning. So if it already exists it simply gives a warning, it's up to the user to ignore it or not.
Thanks in advance!

推荐答案

$key_id = 123;

$result = mysql_query("SELECT * FROM table WHERE key_id='$key_id'");
$num_rows = mysql_num_rows($result);

if ($num_rows) {
   trigger_error('It exists.', E_USER_WARNING);
}

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