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Splunk != vs. NOT Difference Detail Explained with Examples

Different between != and NOT in Splunk search condition, search result and performance impact. How to exclude field from search result?

When you want to exclude results from your search you can use the NOT operator or the != field expression.

However there is a significant difference in the results that are returned from these two methods.

!= vs. NOT Comparison

  • Both!= field expression and NOT operator exclude events from your search, but produce different results
  • Example: status != 200
    • Returns events where status field exists and value in field doesn’t equal 200
  • Example: NOT status = 200
    • Returns events where status field exists and value in field doesn’t equal 200 – and all events where status field doesn’t exist
  • Does != and NOT ever yield the same results?
    • Yes, if you know the field you’re evaluating always exists in the data you’re searching
    • For example:
      • index=web sourcetype=access_combined status!=200
      • index=web sourcetype=access_combined NOT status=200 yields same results because status field always exists in access_combined sourcetype.

Splunk search != vs. NOT result comparison

Searching with != or NOT is not efficient

Using the != expression or NOT operator to exclude events from your search results is not an efficient method of filtering events. The execution cost for a search is actually less when you explicitly specify the values that you want to include in the search results.

Reference

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