Null select query

You'll get a syntax error. Why accept it? Why do you insist it works? With regards to the second piece of code: a count always returns something so it always 'exists'. Yes the first piece of code works now that you have edited it. You might want to edit that bit now. Show 2 more comments. If there are zero records, nothing will be inserted by this code. McDermaid Nick. Add a comment. Sunil Kumar Sunil Kumar 1 1 gold badge 7 7 silver badges 12 12 bronze badges. Sign up or log in Sign up using Google.

Sign up using Facebook. Learn the importance of a great data stack. Discover why our customers rate Chartio 1. Sign up for a day free trial. Learn how your comment data is processed. We will now be looking into a few examples to have a better understanding. Related Posts. Leave a Comment Cancel Reply Your email address will not be published.

Consenting to these technologies will allow us to process data such as browsing behavior or unique IDs on this site. Now, we will apply the missing index suggestion. Without a doubt, the created index is used by the database engine and it boosts the performance of the query because the logical reads number is lower than the previous one. The index seek operator details show us there is not any difference between the Actual Number of Rows and the Estimated Number of Rows.

This situation shows that the query optimizer finds accurate information about how many NULL rows are stored in the MiddleName column.

Most likely, the following question will pop up in your mind. Basically, the statistics store the data distribution about the tables, and the query optimizer makes use of this information during the creation of a query plan. When we create an index this data distribution information is also stored for the NULL valued columns. So that, optimizer estimates how much memory and other resources are required for a query.

As we can see there is an number of NULL values are stored in the MiddleName column and this information is used by the query optimizer.