This is one well documented approach for performance tuning:

http://www.microsoft.com/technet/prodtechnol/sql/bestpractice/performance_tuning_waits_queues.mspx

Try creating a user defined function that returns your next id and then you can call that function from the select statement.

CREATE Function fn_GetId ()

RETURNS INT

AS

   BEGIN

      ...your code here

  ...

If you can do it that way, then eliminate the temp table and simply batch the request

SELECT SUM()

FROM

   (SELECT...

   UNION

   SELECT...)

GROUP BY WHATEVER

Eliminates the extra overhead of the temp table.

You've got it. To add another table to the join is:

SELECT...

FROM Table1 t1

   INNER JOIN Table2 t2

      ON t1.Key=t2.Key

   INNER JOIN Table3 t3

      ON t2.Key2= t3.key2

The reason you can't simply...

Ball park. As indexes degrade, performance tails off because retreiving the data just requires navigating across more pages. Then, as the statistics are more & more out of date as...

By default there's a button that looks like a scroll with a disk in front of it that is "Generate Change Script." Clicking on that button will show the script...

It's a database mail error.

There isn't a single answer to a question like this. I'd start by looking over the best practices as listed by Microsoft here: http://www.microsoft.com/technet/prodtechnol/sql/bestpractice/default.mspx

Specifically some information on storage:

That sounds odd. That's a database mail error. According to BOL either the profile specified doesn't exist or the user running doesn't have permission to access the profile. You may...

Ah, those wonderful 3rd party apps.

I really found next to nothing documented on that process. You may want to open a call with MS. I'd also contact the vendor and...

SP2 seems to introduce almost as many problems as it fixes. That said, if I were doing an install today and didn't face one of the specific issues that SP2...

Since this posted in SQL Server 2005, why not use nvarchar(max)? No problems there, stores the same data.

What about using sp_msforeachdb along the lines of

'SELECT [TABLE_NAME]

FROM ?.INFORMATION_SCHEMA.TABLES'

Substitute where you need to. This works across all the database and eliminates the need for a cursor.

I've mainly grown my best practices over time. We record them locally as we discover new ones that we didn't know we need. MS has some help in this area....

It must be a system proc. There's not only nothing BOL. There's nothing at MSDN. There's nothing at TechNet. There's precious little on a google search. What are you mucking...