Oracle SQL Performance Tuning Best Practices

 Before starting get a clear understanding and quantitative definition of the issue.

Below are some points to be considered for oracle SQL performance tuning   .

• Check for the explain plan, Check for the cost and number of rows that are being fetched.
• Do not include ' * ' in select statements.
• Only select the columns which you need in the query
• Use filters in "WHERE" conditions to restrict the size of the data set.
• Remove unnecessary JOINS.
• Use UNION ALL in case of UNION, Because UNION will perform extra sort operations.
• Avoid the use of IN condition in select statements.
• Avoid the use of the DISTINCT keyword.
• Always use an alias for table names
• If possible use EXISTS in subqueries, it will stop the search when it finds the match. 
• Do not use indexes to tables that undergo more UPDATE or INSERT operations as indexes can slow down the performance in such cases.
• Avoid using VIEWS.
• Don't mix data types and do not convert numbers to characters.
• In some scenarios, we can create a new field rather than performing the calculation on JOIN or WHERE clause.
• Use GLOBAL Temporary tables(GTT), Whenever possible to simplify complication summarization quaries.
• Using of Hints, Hints allows to alter execution plans and force various approhes.