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Remembering that it is good to "get back to basics" every now and then Expand / Collapse
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Posted Tuesday, August 6, 2013 1:35 PM


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I have a new position where I finally have the long sought after Sr. prefix included. Only time will tell if I truly deserve the prefix, but I believe that I can do the job. One of the things that is different about this position by comparison to my most recent projects / positions is a more formalized deployment / implementation process (THANK GOD FOR THIS!!! ). Part of this process is a code review with several other developers that are at least as good as I am...and in many cases better.

I had my first code review today, and the only real issue anyone had with it (aside from learning naming conventions) involved a bit of code that I have used for years on end:
Select VariousFields
Into dbo.TestTable
From dbo.SourceTable(s)

----------
Set @RecordCount =
(Select Count(TestTable_PrimaryKey)
From dbo.TestTable)

The code goes on to split the logic path based on @RecordCount = 0 vs. @RecordCount > 0. This is a section of code that I could have said I had down as well as tying my own shoes (there is a Ted Talks reference there, and this entire post lines up with it).

The conversation went something like this:
Other developer: Why did you use this code here?
Me: Because I was needing to split the logic path.
Other developer: Yes, I see that. What I mean was why didn't you use:
Select VariousFields
Into dbo.TestTable
From dbo.SourceTable(s)

----------
Set @RecordCount = @@RowCount

Me: Because I had never heard of it, thought of it, or seen it before you just typed it.

This post is meant to remind not just me but everyone who reads this to look at those parts of our code that seem all but written in stone that we will use the same approach each time. Is there a better way to do what you're doing?

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Post #1481527
Posted Tuesday, August 6, 2013 2:15 PM


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Interesting story.
I hope they didn't give you the "and you're the senior guy?" look because you didn't memorize all possible TSQL functions.




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Post #1481550
Posted Tuesday, August 6, 2013 2:18 PM


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Thankfully no. The one guy who knew that step was the only one in the room who knew it. All of us in the review were either Sr. or team lead.

“Any fool can know. The point is to understand.”
- Albert Einstein

"DOH!"
- Homer Simpson
Post #1481552
Posted Tuesday, August 6, 2013 2:21 PM


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jarid.lawson (8/6/2013)
Thankfully no. The one guy who knew that step was the only one in the room who knew it. All of us in the review were either Sr. or team lead.


You should try to follow the question of the day here at SSC (if you don't already). Sometimes there's a great question which introduces you to little gems of SQL Server.




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Post #1481553
Posted Tuesday, August 6, 2013 2:45 PM


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Koen Verbeeck (8/6/2013)
You should try to follow the question of the day here at SSC (if you don't already). Sometimes there's a great question which introduces you to little gems of SQL Server.


I've been on the site for years, and I've never been to that before. Thank you. We need a FaceBook style Like button for your post.

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Post #1481566
Posted Tuesday, August 6, 2013 2:54 PM


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no, you should say "Because @@rowcount is affected by any commands in the session, it's my practice to re-select from the table in case there was a trigger that might returna different @@rowcount i might not expect."

just blame force of habit to resolve rare edge cases like that.


Lowell

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Post #1481570
Posted Tuesday, August 6, 2013 2:54 PM
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code goes on to split the logic path based on @RecordCount = 0 vs. @RecordCount > 0.



You shouldn't do a full count of the table for that either, btw; use EXISTS() instead:


IF EXISTS(SELECT TOP (1) 1 FROM dbo.tablename)
BEGIN
--actions to do when table has at least one row
END
ELSE
BEGIN
--actions to do when table has no row
END




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Post #1481571
Posted Tuesday, August 6, 2013 3:37 PM


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Lowell (8/6/2013)
no, you should say "Because @@rowcount is affected by any commands in the session, it's my practice to re-select from the table in case there was a trigger that might returna different @@rowcount i might not expect."

just blame force of habit to resolve rare edge cases like that.


I read this post and thought the same thing. So I decided I should test my theory. It seems that @@rowcount returns the correct number at least in this simple test.

create table RowCountTest
(
id int
)

go

create trigger RowCountTestTrigger on RowCountTest after insert as
select top 1000 *
into #Something
from Tally

go

insert RowCountTest
select 1

select @@ROWCOUNT

If this was a QOTD I would have answered that the value of @@rowcount would be 1000. Interesting. Maybe I will have to do a little more digging and submit as a qotd soon.


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Post #1481587
Posted Tuesday, August 6, 2013 3:53 PM


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Lowell (8/6/2013)
no, you should say "Because @@rowcount is affected by any commands in the session, it's my practice to re-select from the table in case there was a trigger that might returna different @@rowcount i might not expect."

just blame force of habit to resolve rare edge cases like that.

You're partially right about this and is a good thing to know. However, I don't know how a table that was just created by a SELECT...INTO would have any triggers.



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Post #1481594
Posted Tuesday, August 6, 2013 4:27 PM


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Sean Lange (8/6/2013)
Lowell (8/6/2013)
no, you should say "Because @@rowcount is affected by any commands in the session, it's my practice to re-select from the table in case there was a trigger that might returna different @@rowcount i might not expect."

just blame force of habit to resolve rare edge cases like that.


I read this post and thought the same thing. So I decided I should test my theory. It seems that @@rowcount returns the correct number at least in this simple test.

create table RowCountTest
(
id int
)

go

create trigger RowCountTestTrigger on RowCountTest after insert as
select top 1000 *
into #Something
from Tally

go

insert RowCountTest
select 1

select @@ROWCOUNT

If this was a QOTD I would have answered that the value of @@rowcount would be 1000. Interesting. Maybe I will have to do a little more digging and submit as a qotd soon.


An INSTEAD OF trigger can definitely result in @@rowcount being different to SELECT count(x) FROM ...


MM


select geometry::STGeomFromWKB(0x0106000000020000000103000000010000000B0000001000000000000840000000000000003DD8CCCCCCCCCC0840000000000000003DD8CCCCCCCCCC08408014AE47E17AFC3F040000000000104000CDCCCCCCCCEC3F9C999999999913408014AE47E17AFC3F9C99999999991340000000000000003D0000000000001440000000000000003D000000000000144000000000000000400400000000001040000000000000F03F100000000000084000000000000000401000000000000840000000000000003D0103000000010000000B000000000000000000143D000000000000003D009E99999999B93F000000000000003D009E99999999B93F8014AE47E17AFC3F400000000000F03F00CDCCCCCCCCEC3FA06666666666FE3F8014AE47E17AFC3FA06666666666FE3F000000000000003D1800000000000040000000000000003D18000000000000400000000000000040400000000000F03F000000000000F03F000000000000143D0000000000000040000000000000143D000000000000003D, 0);


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