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Columnar Database

The columnar databases store data by columns instead of rows. This means that all values of a single column are stored consecutively on disk. The columns are tied together as “rows” only in a catalog reference. This gives a much finer grain of control to the RDBMS data manager. It can access only the columns required for the query as opposed to being forced to access all columns of the row. It’s optimal
for queries that need a small percentage of the columns in the tables they are in but suboptimal when you need most of the columns due to the overhead in attaching all of the columns together to form the result sets.
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