MySQL：在單個查詢中從數據庫和PHP數組中獲取值

Question

mixed_menu

SELECT mixed.unique_id, 
MENU_LABEL 
      case 
          when (--something...)
FROM mixed_menu mixed 
ORDER BY mixed.position ASC

問題：我想編寫一個mysql查詢，該查詢可以在以下情況下檢索unique_id，MENU_LABEL。

• 情況1：

  如果類型=='db_category'，則從數據庫（ 1.db_category ）中檢索標簽 ，其中id = unique_id

• 情況2：

  如果type =='category'，則從php數組（ 2.PHP Array ）中檢索數組值 ，其中array key = unique_id

---

1. db_category

2. PHP數組

$category_array = array('car'  => 'All Cars', 
                        'jeep' => 'All Jeeps'
                       );

Answer 1

如果您使用php數組創建了一個新表，則會更容易。

但是使用您當前的結構，您可以創建一個臨時/偽表，如下所示

SELECT * FROM (
  SELECT 'car' as `id`, 'All Cars' as `label`
  UNION
  SELECT 'jeep' as `id`, 'All Jeeps' as `label`
) php

因此，您可以使用類似-

SELECT mm.unique_id,

CASE
  WHEN mm.type = 'db_category' THEN dbc.label
  WHEN mm.type = 'category' THEN php.label
END as menu_label

FROM mixed_menu mm

LEFT JOIN db_category dbc ON mm.unique_id = dbc.id

LEFT JOIN (
  /*Create fake table*/
  SELECT 'car' as `id`, 'All Cars' as `label`
  UNION
  SELECT 'jeep' as `id`, 'All Jeeps' as `label`
) php ON mm.unique_id = php.id

ORDER BY mm.position ASC

這里是一個SQLFiddle例子- http://sqlfiddle.com/#!2/5630cc/5

然后，您將需要使用php數組來構建該假表。

編輯

由於您的mixed_menu和db_category表是COLLATION latin1_swedish_ci db_category ，並且使用SELECT UNION默認為COLLATION utf8_general_ci您需要在SELECT UNION聲明它

SELECT * FROM (
  SELECT 'car' COLLATE latin1_swedish_ci as `id`, 'All Cars' COLLATE latin1_swedish_ci as `label`
  UNION
  SELECT 'jeep' COLLATE latin1_swedish_ci as `id`, 'All Jeeps' COLLATE latin1_swedish_ci as `label`
) php    

所以現在查詢將是

SELECT mm.unique_id,

CASE
  WHEN mm.type = 'db_category' THEN dbc.label
  WHEN mm.type = 'category' THEN php.label
END as menu_label

FROM mixed_menu mm

LEFT JOIN db_category dbc ON mm.unique_id = dbc.id

LEFT JOIN (
  /*Create fake table*/
  SELECT 'car' COLLATE latin1_swedish_ci as `id`, 'All Cars' COLLATE latin1_swedish_ci as `label`
  UNION
  SELECT 'jeep' COLLATE latin1_swedish_ci as `id`, 'All Jeeps' COLLATE latin1_swedish_ci as `label`
) php ON mm.unique_id = php.id

ORDER BY mm.position ASC