https://pdfs.semanticscholar.org/08b7/51589c07852ffb4ed689fb634ca0c8b268d0.pdf?_ga=2.245518788.1935701928.1551534105-793639583.1551534105
https://sqlsunday.com/2013/02/19/indexing-basics/
http://www.sqlservercentral.com/articles/Indexing/68439/
https://www.mssqltips.com/sqlservertip/1254/clustered-tables-vs-heap-tables/
https://sqlserverfast.com/epr/merge-join/
https://docs.microsoft.com/ru-ru/sql/relational-databases/pages-and-extents-architecture-guide?view=sql-server-2017
https://blogs.msdn.microsoft.com/craigfr/2006/08/03/merge-join/
https://statisticsparser.com/