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how sql doing inner join

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harshiloh
Starting Member

1 Post

Posted - 2012-05-03 : 07:52:09

1.)please explain the algorithm of sql inner join,

2.)
User table (20 core user)
ID,Name,CityId

City table (1 lakh city)
Id,Name,CountryId

select * from User inner join City on User.CityId=City.Id
select * from City inner join User on User.CityId=City.Id

which one is better ?why?

robvolk
Most Valuable Yak

15732 Posts

Posted - 2012-05-03 : 09:17:39

1. There are 3 types, nested loops, merge, and hash joins. More info on them here:

http://www.sql-server-performance.com/2010/pysical-join-operators/
http://msdn.microsoft.com/en-us/library/ms173815.aspx

2. Neither one is better, they're exactly the same query and will return the same results.

DonAtWork
Master Smack Fu Yak Hacker

2167 Posts

Posted - 2012-05-03 : 11:43:08

Rob: I have an interview coming up. Can you go take it for me? kthksbye!

How to ask: http://weblogs.sqlteam.com/brettk/archive/2005/05/25/5276.aspx
For ultra basic questions, follow these links.
http://www.sql-tutorial.net/
http://www.firstsql.com/tutor.htm
http://www.w3schools.com/sql/default.asp

robvolk
Most Valuable Yak

15732 Posts

Posted - 2012-05-03 : 12:18:06

quote:
Originally posted by DonAtWork

Rob: I have an interview coming up. Can you go take it for me? kthksbye!

Sure! How much are they offering?

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