?
Solved

writing t-sql joins

Posted on 2014-03-25
5
Medium Priority
?
243 Views
Last Modified: 2014-03-25
I can re-write an inner join statement as below:
inner join statement:
  SELECT t1.id, t2.id
  FROM table1 t1
  JOIN table2 t2 on t1.id = t2.id

same statement:
  SELECT t1.id, t2.id
FROM table1, table2
WHERE table1.id = table2.id AND

Are there other joins I rewrite and is there any advantage to doing so?
0
Comment
Question by:dhenderson12
  • 3
  • 2
5 Comments
 
LVL 49

Accepted Solution

by:
PortletPaul earned 2000 total points
ID: 39953171
You should use the top (first) example which is "ANSI join syntax".

The lower example is also allowed and pre-dates adoption of the ANSI standard - but it is a flawed approach and isn't considered best practice today.
0
 

Author Comment

by:dhenderson12
ID: 39953192
why is it a flawed approach?
0
 
LVL 49

Expert Comment

by:PortletPaul
ID: 39953194
why is it flawed? try this:

oops, forgot something - but it still runs as a query (as a Cartesian join)
  SELECT t1.id, t2.id
FROM table1, table2

the equivalent is:
  SELECT t1.id, t2.id
  FROM table1 t1
  JOIN table2 t2 on

it doesn't let you forget the needed conditions.
0
 

Author Comment

by:dhenderson12
ID: 39953203
I see the problem. Thanks.
0
 
LVL 49

Expert Comment

by:PortletPaul
ID: 39953206
& Let me put it another way.

I would not hire anyone who does not use and understand ANSI join syntax. No exceptions.
I (and the company I work for) will not permit non-ANSI syntax in any of our products.

ANSI join syntax is far better for documenting the query logic and for maintaining the SQL.
0

Featured Post

Receive 1:1 tech help

Solve your biggest tech problems alongside global tech experts with 1:1 help.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

When trying to connect from SSMS v17.x to a SQL Server Integration Services 2016 instance or previous version, you get the error “Connecting to the Integration Services service on the computer failed with the following error: 'The specified service …
In this article, we will show how to detach and attach a database and then show how to repair a corrupt database and attach it, If it has some errors. We will show how to detach and attach using SSMS or using T-SQL sentences.
This videos aims to give the viewer a basic demonstration of how a user can query current session information by using the SYS_CONTEXT function
SQL Database Recovery Software repairs the MDF & NDF Files, corrupted due to hardware related issues or software related errors. Provides preview of recovered database objects and allows saving in either MSSQL, CSV, HTML or XLS format. Ensures recov…

593 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question