There are at least 5 ways to return data from one table which is not in another table. Two of these are SQL Server 2005 and greater only. This is a post mostly for beginners but hopefully everyone will get something out of it.

Here are the 5 different ways

NOT IN
NOT EXISTS
OUTER JOIN
OUTER APPLY (2005+)
EXCEPT (2005+)

Let's see how this all works
First create these two tables with the Celko approved naming convention.

CREATE TABLE #testnulls (ID INT)

INSERT INTO #testnulls VALUES (1)

INSERT INTO #testnulls VALUES (2)

INSERT INTO #testnulls VALUES (null)

CREATE TABLE #testjoin (ID INT)

INSERT INTO #testjoin VALUES (1)

INSERT INTO #testjoin VALUES (3)

NOT IN
Run the following Code

SELECT * FROM #testjoin WHERE ID NOT IN(SELECT ID FROM #testnulls)

What happened? Nothing gets returned! The reason is because the subquery returns a NULL and you can't compare a NULL to anything

Now run this

SELECT * FROM #testjoin

WHERE ID NOT IN(SELECT ID FROM #testnulls WHERE ID IS NOT NULL)

That worked because we eliminated the NULL values in the subquery

This also works

SELECT * FROM #testjoin j

WHERE j.ID NOT IN(SELECT ID FROM #testnulls n WHERE n.ID = j.ID)

NOT EXISTS
NOT EXISTS doesn't have the problem that NOT IN has. Run the following code

SELECT * FROM #testjoin j

WHERE NOT EXISTS (SELECT 1

FROM #testnulls n

WHERE n.ID = j.ID)

Everything worked as expected

LEFT and RIGHT JOIN
Plain vanilla LEFT and RIGHT JOINS

SELECT j.* FROM #testjoin j

LEFT OUTER JOIN #testnulls n ON n.ID = j.ID

WHERE n.ID IS NULL

With a RIGHT Join you just switch the tables around

SELECT j.* FROM #testnulls n

RIGHT OUTER JOIN #testjoin j ON n.ID = j.ID

WHERE n.ID IS NULL

SELECT j.* FROM #testnulls n

FULL OUTER JOIN #testjoin j ON n.ID = j.ID

WHERE n.ID IS NULL

AND j.ID IS NOT NULL

You might wonder why we have LEFT and RIGHT Joins, here is why:
<AttemptToBeFunny>LEFT joins are for people who tend to vote for the democrats, RIGHT joins are for people who tend to vote for Republicans. FULL Joins are for independents/undecided people. </AttemptToBeFunny>

You can be real silly and do a subquery LEFT join
 

SELECT j.* FROM #testjoin j

LEFT OUTER JOIN (SELECT ID FROM #testnulls ) n ON n.ID = j.ID

WHERE n.ID IS NULL

Now let's talk about SQL 2005 and up

OUTER APPLY (SQL 2005 +)
OUTER APPLY is something that got added to SQL 2005

SELECT j.* FROM #testjoin j

OUTER APPLY

(SELECT id FROM #testnulls n

WHERE n.ID = j.ID) a

WHERE a.ID IS NULL

EXCEPT(SQL 2005 +)
EXCEPT is something that got added to SQL 2005. It basically returns everything from the top table which is not in the bottom table

SELECT * FROM #testjoin

EXCEPT

SELECT * FROM #testnulls

I am also mentioning INTERSECT since some people might not have seen it before. INTERSECT returns what ever is in both tables(like a regular join)

SELECT * FROM #testjoin

SELECT * FROM #testnulls

So there you have it, most likely you already know all these types of joins. If you learned something from this post that is a good thing also.

It was all going so smoothly. Jason Whittington, Mark Smith and I were teaching the big DevelopMentor event here in Los Angeles (Guerrilla.NET) when my presentation on the ThreadPool took a nose dive. It started with a great joke involving Wilson (the volleyball from Cast Away).

Wilson and I built an application to compute a multiplication table where each computation was (artificially) slow. To speed it up we threw it at the thread pool using delegate.BeginInvoke. We figured that the ThreadPool would allocate 25 or so threads and the table would display quickly. Here's the expected output - pretty much the same thing we've seen since about .NET 1.0:

Each color represents the thread that did that computation.

For the last 7 years, the behavior has been that as the ThreadPool was overloaded, it would steadily start up new threads at the rate of one every 500 milliseconds until it hits its upper limit (typically). Using Performance Monitor (perfmon) we can watch the thread pool adding threads. It usually looks something like this:

Much to our surprise we saw completely different behavior. The thread pool added the first 15 or so threads quickly (as expected) but then stalled. New threads were not created every 500ms, instead they were added at increasingly long intervals. My demo took almost twice as long to run as it had the last time I did this demo a few months ago.

Jason, Mark, and I took this code, ported it back to .NET 1.1 and ran it side-by-side with .NET 3.5 and here's what we saw (blue = 3.5, red = 1.1):

As of .NET 3.5 the upper limit of the ThreadPool was increased: Knew that.

But, it appears that v3.5 of the CLR changes the policy for adding threads to the thread pool. Rather than adding threads regularly when under load the thread pool uses a logarithmic backoff. My colleague Jason Whittington remarked that this behavior looked similar to the behavior of the thread pool in "Rotor" (the shared-source version of the CLR). We speculated that this backoff algorithm makes sense given the new 250-thread per CPU maximum - it would take a long time to reach that if the runtime waits longer and longer to start a new thread. The 250-thread limits makes it less likely that your application will deadlock the thread pool, and the exponential backoff algorithm keeps the thread pool from creating too many threads too quickly.

Why should you care? Usually you won't, but it could have dramatic impact if you count on that behavior. For example, in our contrived case, .NET 1.1 ran about twice as fast as .NET 3.5 ( ! ):

Here's the program and source code (trimmed down to run in both .NET 1.1 and 3.5).

    Math.zip (6.38 KB)

This tutorial explains how to design a beautiful form (Facebook inspired) using a clean CSS design with only <label> and <input> tags to simulate an HTML <table> structure. You can reuse all CSS/HTML elements to design your custom form for your web projects:


Live preview Download this tutorial (HTML + CSS)

Update: I solved an issue with Safari and Firefox, download the new zip file.

Step 1: Input elements and labels
When you design a form (for example to Sign-in or Sign-up on your site), a fast solution to place all form elements in a page is add them into the table's cells. A good and simple alternative is using HTML <input> and <label> tags in this way:

...and the css code is the following:

...in this way, <span> element inside the <label> tag set the same width (70px) for the field descriptions to the left of each <input> element in your form, like if field description and input was placed in a table row with two horizontal cells.

Update: to solve an issue with Safari (using size attribute) and with Firefox (problem to display correctly input label) I changed the following code:

with:

Step 2: Submit Button
When you add a standard/unstyled button in a form (<input> or <button> tag) take a mind it looks different on different browser and OS. A good practice to uniform how it looks is to define a CSS class to apply to your button. Instead of <input> or <button> tag you can also use a simple link (<a> tag) like in this case (I designed and applyed "green" class to the link <a>):

...and CSS code for the "green" class is the following:

The final result is very nice and clean, ready to reuse in your projects.

Download this tutorial (HTML + CSS)