Sql – Understanding SQL Profiler trace

sql serversql-server-profiler

I'm currently experiencing some problems on my DotNetNuke SQL Server 2005 Express site on Win2k8 Server. It runs smoothly for most of the time. However, occasionally (order once or twice an hour) it runs very slowly indeed – from a user perspective it's almost like there's a deadlock of some description when this occurs.

To try to work out what the problem is I've run SQL Profiler against the SQL Express database.

Looking at the results, some specific questions I have are:

The SQL trace shows an Audit Logon and Audit Logoff for every RPC:Completed – does this mean Connection Pooling isn't working?
When I look in Performance Monitor at ".NET CLR Data", then none of the "SQL client" counters have any instances – is this just a SQL Express lack-of-functionality problem or does it suggest I have something misconfigured?
The queries running when the slowness occur don't yet seem unusual – they run fast at other times. What other perfmon counters or other trace/log files can you suggest as useful tools for my further investigation.

Best Answer

Jumping straight to Profiler is probably the wrong first step. First, try checking the Perfmon stats on the server. I've got a tutorial online here:

http://www.brentozar.com/perfmon

Start capturing those metrics, and then after it's experienced one of those slowdowns, stop the collection. Look at the performance metrics around that time, and the bottleneck will show up. If you want to send me the csv output from Perfmon at brento@brentozar.com I can give you some insight as to what's going on.

You might still need to run Profiler afterwards, but I'd rule out the OS and hardware first. Also, just a thought - have you checked the server's System and Application event logs to make sure nothing's happening during those times? I've seen instances where, say, the antivirus client downloads new patches too often, and does a light scan after each update.

Related Solutions

Sql – How to perform an IF…THEN in an SQL SELECT

The CASE statement is the closest to IF in SQL and is supported on all versions of SQL Server.

SELECT CAST(
             CASE
                  WHEN Obsolete = 'N' or InStock = 'Y'
                     THEN 1
                  ELSE 0
             END AS bit) as Saleable, *
FROM Product

You only need to use the CAST operator if you want the result as a Boolean value. If you are happy with an int, this works:

SELECT CASE
            WHEN Obsolete = 'N' or InStock = 'Y'
               THEN 1
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       END as Saleable, *
FROM Product

CASE statements can be embedded in other CASE statements and even included in aggregates.

SQL Server Denali (SQL Server 2012) adds the IIF statement which is also available in access (pointed out by Martin Smith):

SELECT IIF(Obsolete = 'N' or InStock = 'Y', 1, 0) as Saleable, * FROM Product

Sql – Add a column with a default value to an existing table in SQL Server

Syntax:

ALTER TABLE {TABLENAME} 
ADD {COLUMNNAME} {TYPE} {NULL|NOT NULL} 
CONSTRAINT {CONSTRAINT_NAME} DEFAULT {DEFAULT_VALUE}
WITH VALUES

Example:

ALTER TABLE SomeTable
        ADD SomeCol Bit NULL --Or NOT NULL.
 CONSTRAINT D_SomeTable_SomeCol --When Omitted a Default-Constraint Name is autogenerated.
    DEFAULT (0)--Optional Default-Constraint.
WITH VALUES --Add if Column is Nullable and you want the Default Value for Existing Records.

Notes:

Optional Constraint Name:
If you leave out CONSTRAINT D_SomeTable_SomeCol then SQL Server will autogenerate
a Default-Contraint with a funny Name like: DF__SomeTa__SomeC__4FB7FEF6

Optional With-Values Statement:
The WITH VALUES is only needed when your Column is Nullable
and you want the Default Value used for Existing Records.
If your Column is NOT NULL, then it will automatically use the Default Value
for all Existing Records, whether you specify WITH VALUES or not.

How Inserts work with a Default-Constraint:
If you insert a Record into SomeTable and do not Specify SomeCol's value, then it will Default to 0.
If you insert a Record and Specify SomeCol's value as NULL (and your column allows nulls),
then the Default-Constraint will not be used and NULL will be inserted as the Value.

Notes were based on everyone's great feedback below.
Special Thanks to:
@Yatrix, @WalterStabosz, @YahooSerious, and @StackMan for their Comments.