SARGable Queries
You may have seen the term SARGable in blogs or forums and wondered what it means. To start with, SARGable is pseudo-acronym which stands for Search ARGument. A query is considered sargable if the WHERE clause can take advantage of an index to speed up the query. A non-sargable query implies that the WHERE clause (or part of it) cannot use any available indexes which could result in a table or index scan and possibly slow down query performance.
You could possibly have a non-sargable query if you use filters like <>, !=, NOT, NOT IN, LIKE ‘%Clive’, NOT LIKE and NOT EXISTS. These filters could cause the optimiser to not use an index, although not always!
Filters such as =, >, <, <=, >=, IN, LIKE ‘Clive%’ could allow the optimiser to use available indexes to speed up query performance.