Row Compression and Page Compression:
Row Compression:
SQL Server 2008 addresses this issue by introducing a new record format to be used for compressed data that minimizes the overhead of storing the variable length values. It uses only 4 bits of overhead to store the length of the variable length column that is less than or equal to 8 bytes. Note that the previous record format is fully supported in SQL Server 2008 and is the default record format.
page Compression:
Now, if you insert multiple rows into this table, it is possible that many rows will have the same value (i.e. the default) for status column. SQL Server can take advantage of this by storing ‘full time’ value once on the page and then referring to this value from all other occurrences of this value on the same page. As you can imagine, the space savings using this strategy will depend on the amount redundant data on the page.
This strategy is exposed as PAGE compression externally through DDL. A customer can choose to enable ROW or PAGE compression on a table or an index or even on an individual partition(s). PAGE compression includes ROW compression.
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