As explained in Chapter 8, rowstore index column values are stored in the leaf pages of an index’s B-tree structure. Columnstore indexes are also stored in pages, but not within a B-tree structure. When you create an index (clustered or nonclustered) on a table, the cost of data retrieval is reduced by properly ordering the leaf pages of the index and the rows within the leaf pages, whereas a columnstore has the data pivoted into columns and then compressed, again with the intent of assisting in data retrieval. In an OLTP database, data changes continually, ...
14. Index Fragmentation
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