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MySQL query with multiple joins on 7 tables

Posted on 2008-10-29
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Last Modified: 2011-10-19
Hello,

I need help with a query involving 7 tables. I've attached a visual schema that I hope will help.
What I want to do is select all of the documents and display their associated data in each table.

1. Show all the fields in all the records in docs
2. Match docs.doc_cat->category.cat_id to show the cat_name field in category
3. Match docs.doc_origin->origin.origin_id to show the origin field in origin
4. Match docs.doc_id=mapchapters.doc_id AND chapters.chapter_id=mapchapters.chapid to show the chapter field in the chapters table
5. Match docs.doc_id=mapcriteria.doc_id AND criteria.criteria_id=map_criteria.criteria_id to show the criteria field in the criteria table

I was doing fine joning the origin, docs, and category tables,

but when it came to steps 4 and 5 I hit a wall.

each document has 1 category and 1 origin but many criteria and many chapters
document->chapters=many:many
document->criteria=many:many

I hope that I have provided all of the information needed to answer this query, but if not please let me know and I will get back to you right away.
Thanks,
Audg
SELECT * FROM docs AS d1,
LEFT JOIN category AS c1 ON d1.doc_cat=c1.cat_id 
LEFT JOIN origin AS o1 ON d1.doc_origin=o1.origin_id

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archiveschema.jpg
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Question by:aberns
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3 Comments
 
LVL 32

Accepted Solution

by:
Daniel Wilson earned 500 total points
ID: 22834349
You were on the right track ... I think this is your answer.

SELECT d1.*, c1.cat_name, o1.origin, ch.chapter,  cr.criteria
FROM docs AS d1
LEFT JOIN category AS c1 ON d1.doc_cat=c1.cat_id 
LEFT JOIN origin AS o1 ON d1.doc_origin=o1.origin_id
Left Join mapchapters mc on d1.doc_id = mc.doc_id
Left Join chapters ch on mc.chapter_id = ch.chapter_id
left join map_criteria mcr on d1.doc_id = mcr.doc_id
left join criteria cr on cr.criteria_id = mcr.criteria_id

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Author Comment

by:aberns
ID: 22835666
Awesome! It worked! Thanks. I kept thinking I had to define docs with different aliases since I was joining it to multiple tables. Also, is the AS optional? i.e. you have
Join mapchapters mc
but
Join origin AS 01
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LVL 32

Expert Comment

by:Daniel Wilson
ID: 22835699
Yes, I'm pretty sure AS is optional.  I know it is in MS SQL Server ...
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