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Row based / column based Databases

Column format is efficient for analytics (OLAP) because it can limit read access to data to relevant data only.
Row format is efficient for OLTP because it's easy to insert, update or delete records.
Generally, column stores are suitable for read-intensive and large data amounts.
Some claim that column-stores offer better compression (because similar data formats and values go together).

See also

Oracle's columnar-format.

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