Comments on: SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 5 of 31 http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/ Personal Notes of Pinal Dave Fri, 17 May 2013 15:26:57 +0000 hourly 1 http://wordpress.com/ By: Sourish Biswas http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-250430 Thu, 09 Feb 2012 12:40:56 +0000 http://blog.sqlauthority.com/?p=13298#comment-250430 I have seen that DISTINCT affect the performance of any SQL query.
Is there any alternative of DISTINCT which will not affect the performance

]]> By: Sourish Biswas http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-250429 Thu, 09 Feb 2012 12:39:17 +0000 http://blog.sqlauthority.com/?p=13298#comment-250429 1.How can I set the Isolation level as ‘READ UNCOMMITED’?
2.What are the other Isolation levels?
3.Can you provide Syntax or example of it.

4.Also is there anything called Phantom Read. If Yes please explain

]]> By: JeansYang http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-161189 Wed, 24 Aug 2011 01:47:38 +0000 http://blog.sqlauthority.com/?p=13298#comment-161189 Hi pinaldave, I found the Order of the Logical Query Processing Phases in Microsoft.Press.Inside.Microsoft.SQL.Server.2005.T-SQL.Querying.Apr.2006 : (edited special quotes from the book name)

(8) SELECT (9) DISTINCT (11)
(1) FROM
(3) JOIN
(2) ON
(4) WHERE
(5) GROUP BY
(6) WITH {CUBE | ROLLUP}
(7) HAVING
(10) ORDER BY

the order of TOP and ORDER BY is different from what you listed.

]]> By: jj http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-153183 Wed, 03 Aug 2011 14:17:59 +0000 http://blog.sqlauthority.com/?p=13298#comment-153183 When you start with a begin tran and then you run an insert/delete/update, before you run commit tran to complete your insert/delete/update transaction, go to another query analyzer window, do a select statement with nolock hint, you can view that uncommitted data, that is a dirty read also, correct?

]]> By: madhivanan http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-148240 Thu, 14 Jul 2011 11:13:54 +0000 http://blog.sqlauthority.com/?p=13298#comment-148240 In Access, cant you make use of connection string to connect to SQL Server?

]]> By: Rams http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-148018 Wed, 13 Jul 2011 15:41:28 +0000 http://blog.sqlauthority.com/?p=13298#comment-148018 How do we make a connection between Access forms and SQL Server. I know, we can not through link tables. Is there any better way than this.?

]]> By: rams http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-148013 Wed, 13 Jul 2011 15:34:13 +0000 http://blog.sqlauthority.com/?p=13298#comment-148013 yes, dirty read is only happens when Isolation level set to “READ UNCOMITTED”

Thanks,
Ramesh

]]> By: Rahul http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-146122 Tue, 05 Jul 2011 12:32:14 +0000 http://blog.sqlauthority.com/?p=13298#comment-146122 Dirty read is only possible in “READ UNCOMMITTED” isolation level. Please confirm . This question always raise when interviewer is asking about read Phenomena as this happens to me all the time :-) .

]]> By: Ritesh http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-146078 Tue, 05 Jul 2011 07:08:33 +0000 http://blog.sqlauthority.com/?p=13298#comment-146078 Why did U miss the Day 4??

]]> By: NOWISE http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-146075 Tue, 05 Jul 2011 06:16:03 +0000 http://blog.sqlauthority.com/?p=13298#comment-146075 TOUGH TIME !!!

ISN’T IT PINAL ??

]]> By: SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Complete Downloadable List – Day 0 of 31 Journey to SQLAuthority http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-146058 Tue, 05 Jul 2011 04:32:08 +0000 http://blog.sqlauthority.com/?p=13298#comment-146058 [...] SQL SERVER – Interview Questions and Answers – Frequently Asked Questions – Day 5 of 31 [...]

]]> By: pinaldave http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-146042 Tue, 05 Jul 2011 03:26:13 +0000 http://blog.sqlauthority.com/?p=13298#comment-146042 Hi David,

You are correct. I have fixed the issue. The original answer was much longer when edited this was left which was incorrect and confusing. Now fixed.

Thanks again,

]]> By: pinaldave http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-146040 Tue, 05 Jul 2011 03:23:45 +0000 http://blog.sqlauthority.com/?p=13298#comment-146040 I agree with your point Aaron. Very well said. Your comment completes the question. I am updating the question to read your comment.

]]> By: Aaron Bertrand http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-146004 Tue, 05 Jul 2011 01:58:42 +0000 http://blog.sqlauthority.com/?p=13298#comment-146004 I’m only going to touch the IDENTITY section – didn’t read much further than that.

“AutoNumber” is an Access term – be careful suggesting it to potential interviewees for a SQL Server position, especially if Access isn’t on their resume.

I’m not sure how a GUID column generates numbers. I think you meant to specify the UNIQUEIDENTIFIER data type, and specifically one with a default value of NEWID() or NEWSEQUENTIALID(). This is certainly not a number:

639A167C-13F7-46FD-9C99-74DAEB22D12D

You say that the value of an identity cannot be controlled, but I think you need to be more specific. I can reset an identity seed manually via TRUNCATE TABLE or DBCC CHECKIDENT – I can also skip as many rows as I want by issuing inserts and then rolling back. I think what you want to stress here is that you shouldn’t rely on it to produce a continuous sequence of numbers with no gaps.

Finally, you say that identity/GUID columns do not need to be indexed. Like a few of the other comments I think you need to be more specific here; the way I read that statement, it sounds like you are implying they shouldn’t be indexed. Maybe what you meant was that they don’t necessarily need to be indexed, or they don’t necessarily need to participate in the primary key?

If interviewees believe and repeat these things, they will get nowhere.

]]> By: David Ames http://blog.sqlauthority.com/2011/07/05/sql-server-interview-questions-and-answers-frequently-asked-questions-day-5-of-31/#comment-145999 Tue, 05 Jul 2011 01:50:31 +0000 http://blog.sqlauthority.com/?p=13298#comment-145999 Pinal,

What do you mean by ” Identity/GUID columns do not need to be indexed.”?

I’d have thought that 99% of the time, identity/guids form the basis of the primary/foreign key relationships and therefore should be indexed.

]]>