CHAR, VARCHAR, and BINARY columns can be compressed to save disk space. For example, you can compress a column in which large BLOB files such as BMPs and TIFFs are stored. Compression is achieved using the deflate compression algorithm. This is the same algorithm used by the COMPRESS function, and is also the same algorithm used for Windows ZIP files.
Compressed columns can reside inside of encrypted tables. In this case, data is first compressed, and then encrypted.
If a string compresses to a value that is not at least one page smaller than the original value, it is stored uncompressed. Also, strings less than the inline value of the column are not compressed.
To compress columns, use the COMPRESS clause of the CREATE TABLE and ALTER TABLE statements.
You can determine the benefits you are getting by compressing columns using the sa_column_stats system procedure.
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