Functions of the NULL bitmap in SQLSERVER

The role of the NULL bitmap in SQLSERVER first thanks to the articles provided by Song xiaojian and the sqlskill Website :, before reading the following articles, please first read the following two articles: 30 days of SQL Server misunderstanding-Day6-three misunderstandings about NULL bitmap charncharvarcharnvarchar the difference is that bitmap technology is used in many aspects of SQL Server., including

The role of the NULL bitmap in SQLSERVER first thanks to the articles provided by Song xiaojian and the sqlskill Website :, before reading the following articles, read the following two articles: SQL Server misunderstanding on the 30th-Day6-three misunderstandings about NULL bitmap: char nchar varchar nvarchar the bitmap technology is used, including

Functions of the NULL bitmap in SQLSERVER

First of all, I would like to thank song xiaojian for his articles and the sqlskill website. before reading the following articles, please read the following two articles:

30-Day6-three misunderstandings about NULL bitmap in SQL Server

Differences between char nchar varchar nvarchar

Bitmap technology is used in many places inside SQLSERVER, including execution plan, database system page, and NULL bitmap in the Data row mentioned in this article.

Bitmap operators in execution plans

The database system page consists of the DCM page and BCM page. For details, see the DCM and BCM of the SQL Server 2008 storage structure.

The role of these bitmap technologies is undoubtedly to mark

Indicates where changes have occurred. If a change has occurred, it is marked as 1. If no change has occurred, it is marked as 0.

Establish Environment

Create a table

Testnullvarchar (id INT, name varchar (20) NULL) 7 GO