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Query Performance affected by columns selected

user5775242
user5775242 Member Posts: 1
edited May 21, 2015 1:06PM in SQL

I am running an explain plan for a simple query.  If I select columns that are associated with any type of index, the explain plans shows use of the appropriate index.  When I select a column (same where clause) that isn't associated with any index, I get a full table scan in the explain.  Why would the columns in the select statement affect the plan so drastically?  Or is this expected behavior every time you need to get the data from the table, rather than the index?

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