我的这张桌子名为 bag ：
+--------+----------+---------+----------+
| bag_id | chara_id | item_id | item_qty |
+--------+----------+---------+----------+
| 1 | 1 | 2 | 26 |
| 2 | 1 | 1 | 56 |
| 3 | 3 | 1 | 4 |
| 6 | 3 | 4 | 3 |
| 7 | 4 | 4 | 3 |
| 8 | 5 | 4 | 3 |
| 9 | 6 | 4 | 2 |
| 10 | 1 | 5 | 1 |
| 14 | 1 | 8 | 1 |
| 15 | 1 | 6 | 2 |
| 18 | 1 | 4 | 4 |
| 19 | 1 | 3 | 2 |
| 29 | 8 | 1 | 1 |
| 30 | 8 | 7 | 2 |
| 33 | 6 | 2 | 1 |
| 34 | 3 | 5 | 1 |
| 35 | 3 | 8 | 3 |
| 37 | 4 | 3 | 1 |
| 45 | 3 | 3 | 14 |
| 46 | 8 | 2 | 2 |
| 60 | 8 | 5 | 2 |
| 61 | 3 | 2 | 10 |
| 74 | 12 | 2 | 1 |
| 97 | 12 | 5 | 1 |
| 103 | 3 | 6 | 1 |
+--------+----------+---------+----------+
并将此表称为设备：
+----------+----------+-----------+-------------+----------+---------+
| equip_id | chara_id | weapon_id | headgear_id | armor_id | ring_id |
+----------+----------+-----------+-------------+----------+---------+
| 3 | 1 | 4 | 5 | 9 | 8 |
| 5 | 3 | 2 | 5 | 3 | 8 |
| 6 | 4 | 7 | 5 | 3 | 8 |
| 7 | 5 | 4 | 5 | 3 | 8 |
| 8 | 6 | 3 | 5 | 2 | 8 |
| 10 | 8 | 3 | 5 | 2 | 8 |
| 11 | 3 | 2 | 5 | 0 | 8 |
| 12 | 3 | 2 | 5 | 0 | 8 |
| 13 | 12 | 2 | 0 | 0 | 0 |
| 14 | 5 | 4 | 0 | 0 | 0 |
| 15 | 1 | 1 | 0 | 0 | 0 |
| 16 | 1 | 0 | 0 | 6 | 0 |
| 17 | 4 | 4 | 0 | 0 | 0 |
| 18 | 8 | 2 | 0 | 0 | 0 |
| 19 | 3 | 2 | 5 | 0 | 8 |
+----------+----------+-----------+-------------+----------+---------+
情形： 玩家装备从包到设备的物品：
#unequipping:
1. if equipment id to be unequipped exist in the bag then that bag item = item + 1
else
insert that item to the bag
#equipping:
1. bag item = bag item - 1 where item_id = equipped item_id
else if bag item = 0 then delete it.
基本上我想将物品从设备换到袋子表， 虽然扭曲是数量，其中如果要交换的项目已经存在于包表中，那么+ 1到数量，如果包表中的项目是= 1，则从表格中删除该项目并装备该项目设备表。
如果你无法理解我的情况，请告诉我，它让我疯狂！this is my current code(if it helps a little):
$fieldnames = array(1=>'weapon', 'armor', 'ring', 'headgear');
if (isset($fieldnames[$equip->item_type])) {
$field = $fieldnames[$equip->item_type].'_id';
$sql_unequip = "INSERT INTO bag(item_id, chara_id, item_qty)VALUES(:item_id, :chara_id, 1) ON DUPLICATE KEY UPDATE item_qty = item_qty + 1";
$sql_equip = "UPDATE equipment SET $field = :item_id WHERE chara_id = :chara_id";
$sql_unequip2 = "DELETE FROM bag WHERE item_id = :item_id AND chara_id = :chara_id AND item_qty = 0";
}