使用基於恆定值

Question

我有此FF表稱爲設備 SELECT CASE：

+----------+----------+-----------+-------------+----------+---------+ 
| equip_id | chara_id | weapon_id | headgear_id | armor_id | ring_id | 
+----------+----------+-----------+-------------+----------+---------+ 
|  3 |  1 |   3 |   5 |  9 |  8 | 
|  5 |  3 |   3 |   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 | 
+----------+----------+-----------+-------------+----------+---------+ 

，我有這麼長的case語句：

switch ($equip->item_type) { 
     case '1': 
      # Weapon 

      $sql_equip = "UPDATE equipment SET weapon_id = :item_id WHERE chara_id = :chara_id"; 
      break; 

     case '2': 
      # Armor 
      $sql_equip = "UPDATE equipment SET armor_id = :item_id WHERE chara_id = :chara_id"; 
      break; 

     case '3': 
      # Ring 
      $sql_equip = "UPDATE equipment SET ring_id = :item_id WHERE chara_id = :chara_id"; 
      break; 

     case '4': 
      # Headgear 
      $sql_equip = "UPDATE equipment SET headgear_id = :item_id WHERE chara_id = :chara_id"; 
      break; 

     default: 
      # do nothing... 
      break; 
    } 

我在網上看到一些查詢你可以在你的查詢中使用case語句，我搜索了網絡，我似乎找不到一個正確的使用。

我希望它在1語句中，因爲我將它包裝在一個事務函數中，並且還會添加另一行mysql語句。所以，而不是做4x2（當前）我只會做2（如果這可以在1查詢中完成）mysql查詢。

Answer 1

，你可以有這樣的說法，

UPDATE equipment 
SET  weapon_id = CASE WHEN :itemtype = 1 THEN :item_id ELSE weapon_id END, 
     armor_id = CASE WHEN :itemtype = 2 THEN :item_id ELSE armor_id END, 
     ring_id = CASE WHEN :itemtype = 3 THEN :item_id ELSE ring_id END, 
     headgear_id = CASE WHEN :itemtype = 4 THEN :item_id ELSE headgear_id END 
WHERE chara_id = :chara_id 

，但你需要通過三個值，:itemtype，:item_id，:chara_id

Answer 2

$fieldnames = array(1=>'weapon', 'armor', 'ring', 'headgear'); 
if (isset($fieldnames[$equip->item_type])) { 
    $field = $fieldnames[$equip->item_type].'_id'; 
    $sql_equip = "UPDATE equipment SET $field = :item_id WHERE chara_id = :chara_id"; 
}