The search that is enclosed in a square bracket and whose result is passed as a parameter value to the search is called a subsearch. Basically, subsearches are used when the search requires some input that cannot be directly specified or that keeps on changing. Hence, another
search query is written, and the result is passed to the original search.
Let's assume a user wants to know the location and IP address of top three users who have failed the login attempt. Now, the top three users who are failing the login will keep on changing, so subsearches are used. The subsearch will show the top three users that will be passed to the original search. This search will result in the location and IP address of those three users.
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