Question

然而,我担心的是:

$size = isset($_POST[ size ])
  ? " ".mysql_real_escape_string($_POST[ size ])." "
  : "NULL";

$color = isset($_POST[ color ])
  ? " ".mysql_real_escape_string($_POST[ color ])." "
  : "NULL";

if (is_numeric($_POST[ productID ]) && is_numeric($_POST[ amount ]))
{           
  mysql_query("INSERT INTO usercart VALUES (  ,  "
  .mysql_real_escape_string($_SESSION[ user_ID ])." ,  "
  .mysql_real_escape_string($_POST[ productID ])." , "
  .$size." , ".$color." ,  ".mysql_real_escape_string($_POST[ amount ])." )"
  ." ON DUPLICATE KEY UPDATE amount = amount +  "
  .mysql_real_escape_string($_POST[ amount ])." ") or die(mysql_error());
}

在我的我的SQL表一中,有一个独特的索引,名为product>,userID,size and color。但是,当我提出疑问时,它只是插入而不是更新数额。阅读MySQL文件,我可以而且不应该具体指明指数名称。

现在需要几小时左右。因此,谁知道什么?

Answer 1

NULL is always considered unique. So if you set either color or size to null the tuple you re inserting will be considered unique as far as your unique constraints are concerned.

Answer 2

It appears you have a surrogaat key "cart_id", which is also auto increment as the first field. Your fragment will probably result in the DBMS trying to enter user_id into the first field, which is cart_id. Try using a designated insert, omitting the cart_id, like:

INSERT INTO usercart(user_id, product_id, ... )
VALUES (user_id, product_id, ...)
   ;

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