抓取具有关系的数据。 1 个大查询或几个小查询
这样的表结构
假设我有一个像
，我想获取所有用户元数据
，最好进行一次大查询连接图像中的所有表…………
SELECT [columns ...] FROM usermetasections LEFT JOIN usermetakeys ON ...
LEFT JOIN usermetas ON ...
LEFT JOIN users ON ...
WHERE users.id = xxx
或者
将它们分成更小的查询，例如……
Loop through SELECT * FROM usermetasections
Loop through SELECT * FROM usermetakeys WHERE section = xxx
Loop thought SELECT * FROM usermetas WHERE key = xxx AND user = xxx
我认为如果我采用第一种方法，“机器”性能会更快，但对开发人员性能不利？更难阅读，需要更多代码来将查询解析为 PHP 对象？
Suppose I have a table structure like
I want to grab all user metas
is it better to do a big query joining all tables in the image ...
SELECT [columns ...] FROM usermetasections LEFT JOIN usermetakeys ON ...
LEFT JOIN usermetas ON ...
LEFT JOIN users ON ...
WHERE users.id = xxx
...
... or break them into smaller queries like ...
Loop through SELECT * FROM usermetasections
Loop through SELECT * FROM usermetakeys WHERE section = xxx
Loop thought SELECT * FROM usermetas WHERE key = xxx AND user = xxx
I think if I go the 1st approach, it will be faster for "machine" performance but bad for developer performance? harder to read, more code to parse queries into PHP objects?
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通常，您让数据库本身进行连接。这就是关系数据库管理系统的用途。它包含无数的优化，其性能比普通应用程序代码更好。
有时，这确实会在通过网络发送信息方面产生大量开销（例如，您循环超过 1000 条记录，并且仅当满足一些复杂条件时，您才需要来自其他表的信息），在这种情况下，您可以让您的应用程序代码进行连接，但即使如此，您也可以使用
SELECT yourfields FROM yourtables-joined WHERE yourtable.id IN (list,of,IDs)重新查询Usually, you let the database itself do the joining. That's what a relational database management system is made for. It contains countless optimizations that will perform better than your average application code.
Sometimes that does indeed create a lot of overhead in regards to information being sent over the network (say, you loop over 1000 records, and only if a few complex conditions are met, you need the info from the other table) in which case you could let your application-code do the join, but even then you can just re-query with
SELECT yourfields FROM yourtables-joined WHERE yourtable.id IN (list,of,IDs)