Null values database

Everything else is guesswork. Computers are extremely bad at at guesswork: They want facts, and can make desicions based on facts.

Without facts, they are of little or no use Even better, if two or more programmers work on the same table s with NULL values in a database allowed, you could end up with as many different results as you have programmers.

Or more. If you want more documentation on null values in a database, do a Google search: Search for null values. There are depending on your country more than 51 million sites discussing this problem. Yes, the concept of NULL is a problem; just do the search and read on. Don't be surprised if this page shows up as no.

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But is it right; or even better; are NULL values at all allowed at all according to the relational model? 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.

In some cases, the ISNULL function is used with the where condition but this usage method may lead to use indexes inefficiently. This is even the case when the other input is NULL. All that matters is one input is TRUE, the other input, albeit unknown, is irrelevant. Please log in again. The login page will open in a new tab. After logging in you can close it and return to this page. September 5, Good Question! Share 0. Tweet 0. Pin 0. Close dialog. This is what is commonly referred to as a "null pointer".

In a database, zero is a value which has meaning, so the value NULL became is a special marker to mean that no value exists. In that sense, NULL does not refer to a memory location, as it does for programming languages. In a database, the NULL value indicates a lack of a value, which is not the same thing as a value of zero.

To illustrate, consider the question "How many CDs does Rob own?