Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
723 views
in Technique[技术] by (71.8m points)

mysql - In a join, how to prefix all column names with the table it came from

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

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 | ...

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 | ...

Is there a way to achieve this?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

You could

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

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

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

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

(Edited to remove explicit aliases as unnecessary, see comments.)


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...