我想从 EAV(实体属性值)表中提取结果，或者更具体地说是实体元数据表(想像 wordpress wp_posts 和 wp_postmeta)作为格式良好的关系表"，为了进行一些排序和/或过滤.

我找到了一些关于如何在查询中格式化结果的示例(而不是编写 2 个查询并在代码中加入结果)，但我想知道这样做的最有效"方法，尤其是用于更大的结果集.

当我说最有效"时，我指的是以下场景:

获取所有姓氏如 XYZ 的实体

返回按生日排序的实体列表

例如转这个:

** 实体 **----------------------身份证 |姓名 |任何----------------------1 |鲍勃 |等等2 |简 |等等3 |汤姆|等等** 元 **----------------------------------身份证 |实体ID |关键 |价值----------------------------------1 |1 |名字 |鲍勃2 |1 |姓氏 |鲍勃森3 |1 |生日 |1983-10-10.|2 |名字 |简.|2 |姓氏 |简斯多特.|2 |生日 |1983-08-10.|3 |名字 |汤姆.|3 |姓氏 |汤臣.|3 |生日 |1980-08-10

进入这个:

** 结果 **-----------------------------------------------------------开斋节 |姓名 |名字 |姓氏 |生日-----------------------------------------------------------1 |鲍勃 |鲍勃 |鲍勃森 |1983-10-102 |简 |简 |简斯多特 |1983-08-103 |汤姆|汤姆 |汤臣一品 |1980-08-10

所以我可以按任何元字段进行排序或过滤.

我找到了一些建议 这里，但我找不到任何关于哪个效果更好的讨论.

选项:

GROUP_CONCAT:SELECT e.*, GROUP_CONCAT( CONCAT_WS('||', m.KEY, m.VALUE) ORDER BY m.KEY SEPARATOR ';;' )FROM `ENTITY` e JOIN `META` m ON e.ID = m.EntityID

多连接:选择 e.*，m1.VALUE 作为名字"，m2.VALUE 作为姓氏"，m3.VALUE 作为生日"来自实体"e左连接`元`m1ON e.ID = m1.EntityID AND m1.meta_key = '名字'左连接`元`m2ON e.ID = m2.EntityID AND m2.meta_key = '姓氏'左连接`META` m3ON e.ID = m3.EntityID AND m3.meta_key = 'birthday'

合并:选择 e.*, MAX( IF(m.KEY= '名字', m.VALUE, NULL) ) 作为'名字', MAX( IF(m.KEY= '姓氏', m.VALUE, NULL) ) 作为'姓氏', MAX( IF(m.KEY= '生日', m.VALUE, NULL) ) 作为'生日'来自实体"e加入 `META` mON e.ID = m.EntityID

代码:SELECT e.* FROM `ENTITY` e WHERE e.ID = {whatever};

在 PHP 中，从结果中创建一个占位符对象SELECT m.* FROM `META` m WHERE m.EntityID = {whatever};

在 PHP 中，循环遍历结果并附加到实体对象，例如:$e->{$result->key} = $result->VALUE

一般来说哪个更好，用于过滤/排序?

相关问题:

绑定EAV结果如何透视MySQL 实体

解决方案

任何使用数据透视或聚合的东西可能会更快，因为它们不需要表是自联接的.基于连接的方法将需要优化器执行几个子查询操作，然后将结果连接在一起.对于较小的数据集，这可能无关紧要，但如果您对较大的数据集进行分析查询，这可能会显着降低性能，

I want to extract results from EAV (entity-attribute-value) tables, or more specifically entity-metadata tables (think like wordpress wp_posts and wp_postmeta) as a "nicely formatted relational table", in order to do some sorting and/or filtering.

I've found some examples of how to format the results within the query (as opposed to writing 2 queries and joining the results in code), but I would like to know the "most efficient" method for doing so, especially for larger result sets.

And when I say "most efficient", I mean for something like the following scenarios:

Get all Entities with last name like XYZ

Return a list of Entities sorted by birthday

e.g. turn this:

** ENTITY **
-----------------------
ID  | NAME | whatever
-----------------------
 1  | bob  | etc
 2  | jane | etc
 3  | tom  | etc

** META **
------------------------------------
ID | EntityID | KEY         | VALUE
------------------------------------
 1 |   1      | first name  | Bob
 2 |   1      | last name   | Bobson
 3 |   1      | birthday    | 1983-10-10
 . |   2      | first name  | Jane
 . |   2      | last name   | Janesdotter
 . |   2      | birthday    | 1983-08-10
 . |   3      | first name  | Tom
 . |   3      | last name   | Tomson
 . |   3      | birthday    | 1980-08-10

into this:

** RESULTS **
-----------------------------------------------
EID | NAME | first name | last name    | birthday
-----------------------------------------------
 1  | bob  | Bob        | Bobson       | 1983-10-10
 2  | jane | Jane       | Janesdotter  | 1983-08-10
 3  | tom  | Tom        | Tomson       | 1980-08-10

so I can sort or filter by any of the meta fields.

I found some suggestions here, but I can't find any discussion of which performs better.

Options:

GROUP_CONCAT:

SELECT e.*, GROUP_CONCAT( CONCAT_WS('||', m.KEY, m.VALUE) ORDER BY m.KEY SEPARATOR ';;' )
FROM `ENTITY` e JOIN `META` m ON e.ID = m.EntityID

Multi-Join:

SELECT e.*, m1.VALUE as 'first name', m2.VALUE as 'last name', m3.VALUE as 'birthday'
FROM `ENTITY` e
LEFT JOIN `META` m1
    ON e.ID = m1.EntityID AND m1.meta_key = 'first name'
LEFT JOIN `META` m2
    ON e.ID = m2.EntityID AND m2.meta_key = 'last name'
LEFT JOIN `META` m3
    ON e.ID = m3.EntityID AND m3.meta_key = 'birthday'

Coalescing:

SELECT e.*
   , MAX( IF(m.KEY= 'first name', m.VALUE, NULL) ) as 'first name'
   , MAX( IF(m.KEY= 'last name', m.VALUE, NULL) ) as 'last name'
   , MAX( IF(m.KEY= 'birthday', m.VALUE, NULL) ) as 'birthday'
FROM `ENTITY` e
JOIN `META` m
    ON e.ID = m.EntityID

Code:

SELECT e.* FROM `ENTITY` e WHERE e.ID = {whatever};

in PHP, create a placeholder object from result

SELECT m.* FROM `META` m WHERE m.EntityID = {whatever};

in PHP, loop through results and attach to entity object like: $e->{$result->key} = $result->VALUE

Which is better in general, and for filtering/sorting?

Related questions:

Binding EAV results How to Pivot a MySQL entity

解决方案

Anything using pivot or aggregates will probably be faster, as they don't require the table to be self-joined. The join based approaches will require the optimiser to perform several sub-query operations and then join the results together. For a small data set this might not matter so much, but this could significantly degrade performance if you're doing an analytic query on a larger data set,