Difference between the NOT and != operators?

[Jason]

What is the difference between the NOT operator and the != operator?

I have always used NOT up to this point, but am seeing some very strange behavior associated with it today* and != seems to function as I intend.

NOT seems to be adding seemingly unrelated terms to litsearch in the search inspector's "remote search" which cause the search to fail

[zac]

Most Simplified Explanation

!= is a field expression that returns every event that has a value in the field, where that value does not match the value you specify. Events that do not have a value in the field are not included in the results. For example, if you search for Location!="Calaveras Farms", events that do not have Calaveras Farms as the Location are returned. Events that do not have Location value are not included in the results.

On the other hand, NOT is an operator that returns every event except the events that contain the value you specify. This includes events that do not have a value in the field. For example, if you search using:

 NOT Location="Calaveras Farms", every event is returned except the events that contain the value “Calaveras Farms”. This includes events that do not have a Location value.

Here’s an example to illustrate the difference between the two methods. Suppose you have the following events:

Table

ID Name Color Location

101M3	McIntosh	Chestnut	Marin Meadows
104F5	Lyra	Bay
104M6	Rutherford	Dun	Placer Pastures
101F2	Rarity		Marin Meadows
102M7	Dash	Black	Calaveras Farms
102M1	Roan
101F6		Chestnut	Marin Meadows
104F4	Pinkie	Sorrel	Placer Pastures

If you search with Location!="Calaveras Farms", every event that has a value in the Location field, where that value does not match Calaveras Farms, is returned. Events that do not have a value in the Location field are not included in the results. The following events are returned:

Output Table

ID Name Color Location

101M3	McIntosh	Chestnut	Marin Meadows
104M6	Rutherford	Dun	Placer Pastures
101F2	Rarity		Marin Meadows
101F6		Chestnut	Marin Meadows
104F4	Pinkie	Sorrel	Placer Pastures

If you search with NOT Location="Calaveras Farms", every event is returned except the events that contain the value Calaveras Farms. This includes events that do not have a Location value. The following events are returned:

Output Table

ID Name Color Location

101M3	McIntosh	Chestnut	Marin Meadows
104F5	Lyra	Bay
104M6	Rutherford	Dun	Placer Pastures
101F2	Rarity		Marin Meadows
102M1	Roan
101F6		Chestnut	Marin Meadows
104F4	Pinkie	Sorrel	Placer Pastures

[Ayn · Accepted solution]

The difference is that with != it's implied that the field exists, but does not have the value specified. So if the field is not found at all in the event, the search will not match.

NOT field= on the other hand will check if the field has the specified value, and if it doesn't for whatever reason, it will match.

(from http://splunk-base.splunk.com/answers/43228/use-of-not-vs )

[linu1988]

From my point of view, NOT is like a logical operator rather than the exact "Not equal to operator" which should be considered as an arithmetic operator. Internally it should work like that as other languages, but sometimes it's output makes us think them the same.

[Jason]

Well, that mentions they're different, I want to know how they're different, why one (NOT) added some unnecessary terms to litsearch that broke one of my searches when the other (!=) did not.

[RohiniJindam]

Possibly what you're looking for

Difference between NOT and !=