Question

php+mysql怎样查询在user表内是否有和$_POST[id]相同 的字段值？

Answer 1

$id = intval($_POST['id']);

$result = mysql_query("SELECT COUNT(1) FROM user WHERE id=$id");
$ufound = mysql_fetch_row($result);
if ($ufound[0] > 0) { echo "id: $id 已存在"; }

Answer 2

select 想要查询的字段 from user where 想要查询的字段=$_POST[id]

Answer 3

$sql="select * from user where 字段=$_POST[id];