what is the different between below two ways when join three SQL tables?

Question

0.00/5 (No votes)

See more:

I have 3 tables SalesPerson, Customer and Orders
I got the same result from below queries by using join and not. Can anyone please explain , what are the differences and similarities of below two ways? Why join if we can do the same thing without join?

1) select s.name
from SalesPerson s, Orders o, Customer c
where s.sid = o.sid and
c.cid = o.cid and
c.name = 'Samsonic'

2) select s.name
from Orders o
Inner Join SalesPerson s
on s.sid = o.sid
Inner Join Customer c
on c.cid = o.cid
where c.name = 'Samsonic'

Posted 25-May-15 23:32pm

Prabhani Panamulla

Updated 25-May-15 23:33pm

v2

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Advay Pandya · Accepted Answer · 2015-05-26T00:15:00

Hello,

it's nice question.

The only difference in both of the query is performance.

If you use JOIN statement then it will give faster result then WHERE statement.

I tried to execute both kind of queries in a database having huge amount of data and I noticed much difference in execution time.

I think, if we use WHERE condition then first SQL will fetch all the data and then apply WHERE condition. and If we use JOIN statement then SQL will consider only data which satisfy the condition in ON keyword.

But, the difference is only performance of SQL queries.

Please share your thoughts on this.

Thanks
Advay Pandya

willington.d · Accepted Answer · 2015-05-26T00:00:00

Solution 1

There is no difference. The first one is old standered.

Reference:http://www.sqlservercentral.com/Forums/Topic262270-8-1.aspx[^]

Posted 26-May-15 0:00am

willington.d

Comments

Prabhani Panamulla 26-May-15 6:12am

thanks a lot.