Transaction count during DML statements

Recently I was troubleshooting a blocking problem where a number of sessions were blocked, waiting to acquire a page latch. While blocking was occurring, there were several rows in the output from sysprocesses that looked like this (only relevant columns are shown): spid   status     blocked open_tran waitresource  cmd     lastwaittype —— ———- ——- ——— ————- ——-…

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Disjoint subtyping in SQL

Disjoint subtyping is a scenario that is often encountered in data modeling. In one frequently used modeling approach, an entity of a certain type is represented by a database table, and each subtype of this entity is represented by another table. Subtyping is disjoint if an instance of a type corresponds to at most one…

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Surrogate keys in distributed databases

In this post, the term “distributed database” refers to a set of SQL Server databases, each managed by a SQL server running on a separate computer. All databases have identical schemas, and data that originates in one database is replicated to all other databases, or nodes. A common example would be a system with a…

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