When is null sql

Asked 11 years, 4 months ago. Active 5 months ago. Viewed k times. Add a comment. Active Oldest Votes. Kirk Woll Marcelo Cantos Marcelo Cantos k 37 37 gold badges silver badges bronze badges. It's marginally less efficient, but much more elegant.

In the end, you have the same result. If you need to optimize, check the execution plans but I have not noticed much of a difference. Nordic Mainframe Nordic Mainframe I didn't know that.

Haven't thought that there are so much possibilities to do that. There are plenty of solutions but none covers why the original statement doesn't work.

NeatNit 1 1 gold badge 2 2 silver badges 12 12 bronze badges. Ian Jacobs Ian Jacobs 5, 1 1 gold badge 22 22 silver badges 37 37 bronze badges.

Yeah realized it after I posted. Figured I'd leave it since it solved the part he was having trouble with. The problem is that null is not considered equal to itself, hence the clause never matches. Something unknown, is most likely not the same as something else that is unkown. Found a solution to this.

Paul Roub For this reason, working with the NULL values might be a bit complicated and are required to use certain built-in functions which are customized for handling NULL values. The expression parameter indicates the expression which we want to check NULL values.

The replacement parameter indicates the value which we want to replace the NULL values. When we use this function with the star sign it count all rows from the table regardless of NULL values. Such as, when we count the Person table through the following query, it will return When we calculate the weekly average fee, the Wednesday fee is not included in the calculation.

On the other hand, when we try to use an equal operator to find the rows that contain the null values, the result set will return nothing. For example, the following query will not return any rows. The reason for this issue is related to the structure of the SQL NULL because it does not specify an explicit value thus comparing an unknown value with an exact value result will be false.

The indexes can help to improve the performance of the queries but at this point, one question may appear in our minds. When we execute the following query, the query optimizer suggests a non-clustered index and it claims that this index dramatically improves the performance of the query. As seen in the execution plan, the optimizer has decided to use a non-clustered index scan operator, and it reads data pages from the data cache.

If you want to report an error, or if you want to make a suggestion, do not hesitate to send us an e-mail:. Exercise: Select all records from the Customers where the PostalCode column is empty. Report Error. Your message has been sent to W3Schools. W3Schools is optimized for learning and training.