What does the coalesce command mean in this Splunk search?

[pavanae]

What does the below coalesce command mean in this Splunk search? Any explanation would be appreciated

eval fieldA=coalesce(fieldA,"")

[gcusello]

Hi pavanae,
are you sure that this function runs?
every way, coalesce "takes an arbitrary number of arguments and returns the first value that is not null", so there is no sense to put a null value in this function (see http://docs.splunk.com/Documentation/Splunk/6.3.1/SearchReference/CommonEvalFunctions).
If you want to give to FieldA a different value when it's null, you have to use eval FieldA=if(isnull(FieldA),"X",FieldA).
Bye.
Giuseppe

[richgalloway]

An empty string ("") is not the same as a null value.

[richgalloway · Accepted solution]

The coalesce command is essentially a simplified case or if-then-else statement. It returns the first of its arguments that is not null. In your example, fieldA is set to the empty string if it is null. See http://docs.splunk.com/Documentation/Splunk/6.5.0/SearchReference/CommonEvalFunctions.