在联接中，如何在所有列名之前添加其来源表的前缀 [英] In a join, how to prefix all column names with the table it came from

问题描述

我正在分析一个相当糟糕的旧数据库/代码库，试图通过将查询合并到联接中来减少服务器负载(包括电子邮件警报cron作业，该作业通常会调用超过一百万个单独的查询).

I'm analysing a rather horrible legacy database/codebase, trying to reduce server load by combining queries into joins (including an email alert cron job that typically invokes well over a million separate queries).

SELECT * FROM 
class_alerts_holding ah 
INNER JOIN class_listings l ON l.id = ah.lid 
INNER JOIN class_users u ON u.id = ah.uid
LEFT JOIN class_prodimages pi ON pi.pid = ah.lid

这会吐出120列...

This spits out 120 columns...

aid | id | lid | uid | oid | catName | searchtext | alertfreq | listType | id | owner | title | section | shortDescription | description | featured | price | display | hitcount | dateadded | expiration | url | notified | searchcount | repliedcount | pBold | pHighlighted | notes | ...

为了帮助我分析如何构造新查询，如果我可以在结果中的列前面加上来自JOIN的表的前缀，那将是很棒的事情.

To assist my analysis of how to construct the new queries it would be awesome if I could prefix the columns in the result with the table they came from in the JOIN e.g.

class_alerts_holding.aid | class_alerts_holding.id | class_listings.lid | ...

有没有办法做到这一点?

Is there a way to achieve this?

推荐答案

您可以

select ah.*, l.*, u.*, pi.* from ...

那么这些列将至少按表的顺序返回.

then the columns will be returned ordered by table at least.

为了更好地区分每两组列，您还可以像这样添加定界符"列:

For better distinction between every two sets of columns, you could also add "delimiter" columns like this:

select ah.*, ':', l.*, ':', u.*, ':', pi.* from ...

^{(已编辑，删除了不必要的显式别名，请参见注释.)}

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