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If I saw a data model where a table had 2.1 million rows, one of the columns had only 5 distinct values, and I knew that people wanted to get a listing of those distinct values on a somewhat regular basis, I would strongly suspect that the data model was missing a lookup/ dimension table. Rather than trying to tune your current query, I would bet that the ...


If Oracle only scans the index it cannot decide if there is a row with NULL in this column. So it makes a full table scan. A possible workaround: create a bitmap index on column4. This index contains the NULL columns, too. More details can be found in this post Why isn't oracle using an index for distinct query ?


when you are installing oracle database you can install all oracle example schemas like scott, HR, oe ... you can install these in step "Specify Database Config Details".click the last tab page "Sample Schemas" then check the check box "create database with sample schemas" as displayed bellow in screenshot. if you already installed database you can ...

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