Question

我需要找到一种方法来“连接”两个字段（类似于key =＆gt; value）。例如，在该查询中，我想仅显示其中的项目（fielddef_id = 4 =＆gt; fieldval.value =“Documentstéléchargeables”）AND（fielddef_id = 5 =＆gt; fieldval.value =“Anglais”）。

表fielddef存储密钥表fieldvalue存储值

但是有很多组合：key = value ...（例如：lang = English，type = downolad）

SELECT item.item_id AS id, item.title AS title, item.active AS active, item_cat.category_id AS cat_id, item_cat.item_id AS item_id, category.category_id, category.category_name as cat_name, category.category_alias as cat_alias 
FROM `cms_module_listit2ressources_item` AS item 
LEFT JOIN `cms_module_listit2ressources_item_categories` AS item_cat 
ON item.item_id = item_cat.item_id 
LEFT JOIN `cms_module_listit2ressources_category` AS category 
ON item_cat.category_id = category.category_id 
LEFT JOIN `cms_module_listit2ressources_fieldval` AS fieldval 
ON item.item_id = fieldval.item_id 
LEFT JOIN `cms_module_listit2ressources_fielddef` AS fielddef 
ON fieldval.fielddef_id = fielddef.fielddef_id
WHERE item.active=1 
AND (fielddef.fielddef_id="4" AND fieldval.value IN ("Documents tÃ©lÃ©chargeables")) 
AND (fielddef.fielddef_id="5" AND fieldval.value IN ("Anglais"))

这是一个简单的例子，让你知道我想做什么...请注意我无法改变数据库的概念

TABLE ITEMS Store the ID and Title of an item.
id= INT / Primary / auto_increment
title = VARCHAR (255)

每个项目都有许多自定义字段（例如：“color = red”，“Country = France”等。）

TABLE CUSTOM_FIELDNAME Stores the fieldname (definition => example : "Color", "Country")
fielddef_id = INT / PRIMARY / auto_increment
name = VARCHAR(255) (=> ex: Color, Country...)

TABLE CUSTOM_FIELDVALUE stores the field value (example : "red", "France")
item_id => foreign_key to link to the ITEMS TABLE
fielddef_id => foreign_key to link to the CUSTOM_FIELDNAME TABLE
value = VARCHAR(255) (=> ex: red, France...)

我只需列出项目WHERE color = red AND Country = FRANCE

示例数据：

TABLE ITEMS :
id=1 | Title = "first Item"
id=2 | Title = "A red French Item"

TABLE CUSTOM_FIELDNAME
fielddef_id = 1 | name = "Color"
fielddef_id = 2 | name = "Country"

TABLE CUSTOM_FIELDVALUE
item_id = 1 | fielddef_id = 1 | value = "Blue"
item_id = 1 | fielddef_id = 2 | value = "Germany"
item_id = 2 | fielddef_id = 1 | value = "Red"
item_id = 2 | fielddef_id = 2 | value = "France"

所以我的查询如下：

SELECT items.title AS title
custom_fieldname.name as customName
custom_fieldvalue.value as customValue
FROM `items`
LEFT JOIN `custom_fieldvalue`
ON items.id = custom_fieldvalue.item_id 
LEFT JOIN `custom_fieldname`
ON custom_fieldvalue.fielddef_id = custom_fieldname.fielddef_id 
WHERE(custom_fieldname.fielddef_id="1" AND custom_fieldvalue.value "Red") AND (custom_fieldname.fielddef_id="2" AND custom_fieldvalue.value "France")

Answer 1

首先， DON＆＃39; T 将条件放在LEFT JOIN子句中WHERE的右表中，它们只应放在{{1}中}。clause。

其次，你的最后一个条件没有意义，并且永远是ON()，一个字段一次不能超过1个值。

第三，字符串比较应使用单引号FALSE而非双'。

最后，你应该使用"，尝试这样的事情（我假设你必须稍微调整一下）：

CONCAT()

Answer 2

E.g：

SELECT i.item_id AS id
     , item.title AS title
     , item.active AS active
     , item_cat.category_id AS cat_id
     , item_cat.item_id AS item_id
     , category.category_id
     , category.category_name as cat_name
     , category.category_alias as cat_alias 
     , v4.value v4_value
     , d4.fielddef_id d4_fielddef_id
     , v5.value v5_value
     , d5.fielddef_id d5_fielddef_id
  FROM cms_module_listit2ressources_item i
  LEFT 
  JOIN cms_module_listit2ressources_item_categories ic
    ON ic.item_id = i.item_id 
  LEFT 
  JOIN cms_module_listit2ressources_category c
    ON c.category_id = ic.category_id 
  LEFT 
  JOIN cms_module_listit2ressources_fieldval v4
    ON v4.item_id = i.item_id 
   AND v4.value IN ("Documents téléchargeables") 
  LEFT 
  JOIN cms_module_listit2ressources_fielddef d4
    ON d4.fielddef_id = v4.fielddef_id
   AND d4.fielddef_id = 4 
  LEFT 
  JOIN cms_module_listit2ressources_fieldval v5
    ON v5.item_id = i.item_id
   AND v5.value IN ("Anglais")
  LEFT 
  JOIN cms_module_listit2ressources_fielddef d5
    ON d5.fielddef_id = v5.fielddef_id 
   AND d5.fielddef_id = 5 
 WHERE i.active = 1;

具有联合和自定义字段的复杂mySQL查询

2 个答案: