Plsql null value

Steven Feuerstein February 18, at AM. Jan March 6, at AM. Steven Feuerstein March 6, at AM. Popular posts from this blog. Get rid of mutating table trigger errors with the compound trigger. December 13, When something mutates, it is changing. Something that is changing is hard to analyze and to quantify. In particular, this error occurs when a row-level trigger attempts to read or write the table from which the trigger was fired.

Fortunately, the same restriction does not apply in statement-level triggers. In this post, I demonstrate the kind of scenario that will result in an ORA errors. I then show the "traditional" solution, using a collection defined in a package. Then I demonstrate how to use the compound trigger, added in Oracle Database 11g Release1, to solve the problem much more simply.

In the case you've given you also have the option of using the NVL built-in function. NVL takes two arguments, the first being a variable and the second being a value constant or computed.

So you could rewrite. And because it's nearly ten years since I wrote this answer, let's celebrate by expanding it just a bit. It takes any number of arguments, and returns the first one which is not NULL. Best way to avoid them is to use nvl. 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. Check if a variable is null in plsql Ask Question. Asked 12 years ago. Connect and share knowledge within a single location that is structured and easy to search. I'm using a IF condition to check whether 2 values are equal or not. How Can I compare values in this kind of situations. I presume there might be different combinations of non-null and null values.

One option is to check them all, or - maybe simpler - use NVL , such as:. Depending on datatypes, you might need to use something else, not 0. 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. The following queries will never return any rows, regardless of the contents of the employees table. Of course, you will rarely write code that includes explicit references to the NULL literal. You are more likely to see and write code like this:. That might be fine, but you need to give consideration very deliberately to these questions: "Could a null value be passed in here? Should I allow a null value to be passed here?

Then take the necessary steps to bulletproof your code from nulls see last section in this blog post for details. When a row is inserted into and updated in this table, the following columns cannot be set to NULL :. Wait, you might be saying: Why do you have to provide a value for ID? That's because identity columns can never be set to NULL. Identity columns are new to That behavior is shown in the code below. Instead, you must use a datatype that cannot be null or add code to your subprogram to "protect" it from null values.

See the section Bulletproofing for Nulls below. Oracle Database currently treats a character value with a length of zero as null. However, this may not continue to be true in future releases, and Oracle recommends that you do not treat empty strings the same as nulls.

But we encourage you to not write code that assumes that this will always be the case. Whenever you declare a variable, it's value is set to NULL — unless you assign a different value to it.

So, yes, you could do the following:. But I suggest that you do not. Don't worry; Oracle is never going to change this behavior, so you don't have to "take out insurance.