2012:
https://docs.microsoft.com/zh-cn/previous-versions/sql/sql-server-2012/ms175049(v%3Dsql.110)
2017:
https://docs.microsoft.com/zh-cn/sql/2014/relational-databases/indexes/indexes?view=sql-server-2017
https://www.cnblogs.com/knowledgesea/archive/2013/01/02/2841588.html