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Oracle not equals (!=) SQL operator

Oracle Tips by Burleson Consulting


There are many ways to express the same syntax in Oracle SQL and the "not equals" operator may be expressed as "<>" or "!=".

You can also use the "not exists" or the "minus" clause in SQL.  See Tips on using NOT EXISTS and MINUS in SQL

These "not equal" operators are supposed to be equivalent, but this note by Scott Canaan suggests that in Oracle 10.2, they can produce different execution plans, and hence, different execution speeds:

Select count(*) from claws_doc_table where claws_doc_id = :id and exists
(select 1 from claws_person_id where status != 0);


If you use !=, it returns sub-second. If you use <>, it takes 7 seconds to return. Both return the right answer.

 

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Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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