How can queries be written to perform the fastest when equality and inequality comparisons are needed?
Equality comparisons are generally faster than inequality comparisons. For example, P_PRICE = 10.00 is processed faster because the DBMS can do a direct search using the index in the column. If there are no exact matches, the condition is evaluated as false. However, if an inequality symbol (>, >=, <, <=) is used, the DBMS must perform additional processing to complete the request, because there will almost always be more "greater than" or "less than" values in the index than "equal" values. With the exception of NULL, the slowest of all comparison operators is LIKE with wildcard symbols, as in V_CONTACT LIKE "%glo%". Also, using the "not equal" symbol (<>) yields slower searches, especially when the sparsity of the data is high—that is, when there are many more different values than there are equal values.
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