data-konzept

'Accelerated Database Recovery (ADR) is a new SQL database engine feature that greatly improves database availability, especially in the presence of long running transactions, by redesigning the SQL database engine recovery process. ADR is currently available for single databases, elastic pools, and Azure SQL Data Warehouse. The primary benefits of ADR are:

• Fast and consistent database recovery

  With ADR, long running transactions do not impact the overall recovery time, enabling fast and consistent database recovery irrespective of the number of active transactions in the system or their sizes.

• Instantaneous transaction rollback

  With ADR, transaction rollback is instantaneous, irrespective of the time that the transaction has been active or the number of updates that has performed.

• Aggressive log truncation

  With ADR, the transaction log is aggressively truncated, even in the presence of active long running transactions, which prevents it from growing out of control.'...

https://docs.microsoft.com/en-us/azure/sql-database/sql-database-accelerated-database-recovery

'One thing that is often handy is to know how much space each table is using within your database. It is helpful to know the number of rows, the data space used as well as the index space used. There are several ways that you can get this information, by reading the system tables, using SSMS and using the built-in reports in SSMS. In this tip we look at some queries that can be used to do this.'...

https://www.mssqltips.com/sqlservertip/1177/determining-space-used-for-all-tables-in-a-sql-server-database/

'The ability to combine results from related rows from multiple tables is an important part of relational database system design. In SQL Server, this is accomplished with the SQL join clause.  It’s the nature of traditional relational database systems where some table contains information related to other tables with a common key value. Using a SQL join, you can easily perform queries on related data-sets from multiple tables with these shared keys.

The aim of this article is to provide you with the basic knowledge and examples that you will need to use the SQL join effectively in any database environment.'...

https://www.sqlshack.com/sql-join-overview-and-tutorial/

'While the difference is very important 90% of the time you won’t care and should just add the two numbers together.

I/O and Logical I/O are two pieces of information you will see all over the place. 

• SET STATISTICS IO as physical reads and logical reads

• sys.dm_exec_requests and sys.dm_exec_sessions as reads and logical_reads

• sys.dm_exec_procedure_stats and sys.dm_exec_query_stats as x_logical_readsand x_physical_reads 

Just to name a few.

There is an important difference between the two. Physical reads/IO are page reads from the disk. Logical reads/IO are pages read from memory. So why do we care? Reading from the disk is massively slower than reading from memory. '...

https://sqlstudies.com/2018/09/05/i-o-vs-logical-i-o/