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Equals: =
This one is the most efficient SQL query, especially if the WHERE clause is covered by an index.
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Greater than, less than: >, >=, <, <=, BETWEEN
Note that Microsoft SQL Server rewrites a BETWEEN to >= and <=.
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Like: LIKE
Note that if you start with a wildcard, then SQL Server will do a table scan, whether there is an index or not, such as: LIKE '%E'.
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Different from: <>, NOT
Note that Microsoft SQL Server rewrites a NOT to <>.
Note that SQL Server will do a table scan, whether there is an index covering the WHERE clause or not.
So, use = as much as possible and use <> as least as possible.
If you're going to be doing a lot of "leading wild card" lookups (like '%E'), index the reverse of your column and look up 'E%' in the reverse.