There is no defined limit to the number of characters in a query. For number of words, a good rule of thumb is 8,000. Some EBSCOhost databases will allow up to 40,000 words, which can be necessary to run queries generated from search-history entries combined with heavy use of truncations with wildcard expansions. The use of a wildcard character (the asterisk) with truncation expands a word in a query up to a limit of 2000 expansions. If you enter a short truncated search term, (such as nu*), the search engine will look for all words beginning with “nu” (such as nut, numb, nugget nurse, nursing, etc.) and expand the search term up to a maximum of 2000 variations. When constructing long queries with wildcard truncation and proximity operators, use compact query syntax for better performance and more readable queries.
How do I create a proximity search using EBSCOhost?