Sql query null check

Please see Oracle code below. If you are writing a trigger you generally don't bother checking if anything exists in the pseduo table, you just write the code based off the pseudo table. Also note that oracle triggers perform row by row and SQL Server triggers are called once, with possibly mutliple records in psuedo tables.

It contains all records inserted or updated. There might be 0,1, or many records in here. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 7 years, 5 months ago. Active 6 years, 11 months ago. Viewed 62k times. Improve this question. I really can't think of a case for this, unless you use it in a subquery and join it. You'll get better results than with these contrived examples. Also keep in mind a query never returns NULL. A column does. Show 10 more comments. 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.

However, this query cannot use the created non-clustered index so it will read all index pages and then return the appropriate rows. To eliminate this situation, we can make a little code modification in the query so that the query optimizer can use the indexes more efficiently. The following query returns some rows as like the previous one but it uses the indexes more efficiently. FROM Person. USE [ AdventureWorks ]. Therefore, all string values that consist entirely of spaces including zero spaces will be deemed to be equal e.

Finally, from the above different code you understand regarding how do you check if a column is blank or Null in SQL. Hey there! Some links on this page are affiliate links which means that, if you choose to make a purchase, I may earn a small commission at no extra cost to you. I greatly appreciate your support!