Join synopsis?

[MorganGreylock]

Could someone possibly post (or post a link to) a synopsis of the different types of joins (left, right, inner, outer, etc)
and what they do and when to use them? I've searched the web for some documentation, but most of the sites I've seen don't even enough examples for me to determine what it is I need to do.

It would also just be very useful knowledge and reference...

Thanks in advance,
MG

 

[PruSQLer]

Which relational Database will you be using?

 

[MorganGreylock]

I didn't think it would matter, but in this project I am using postgresql on redhat linux.

MG

 

[PHV]

The nature of the join depends on the cardinality of the relation between the 2 tables.

Hope This Help, PH.
Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884

 

[PruSQLer]

Yes, joins are pretty much the same in any database but most of the stuff I know of is geared to DB2. Here's a link to a site which has a download that includes a good section on joins.

http://ourworld.compuserve.com/homepages/graeme_birchall/HTM_COOK.HTM

If you want some detailed stuff on outer joins, I can send you email.

 

[PHV]

AFAIK, outer joins are for 0-1 or 0-n relations.

Hope This Help, PH.
Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884

 

[r937]

AFAIK, outer joins are for 0-1 or 0-n relations.

not necessarily

you could have a 1-n relationship, for example between students and courses (student must have at least one course, so it's 1-n not 0-n) and yet still want to run a left outer join to find students who don't take math

rudy

http://r937.com/

SQL Consulting

 

[r937]

I didn't think it would matter

it doesn't

Understanding SQL Joins (mysql)

rudy

http://r937.com/

SQL Consulting