Count and group by in adventureworks2012

#COUNT AND GROUP BY IN ADVENTUREWORKS2012 CODE#

The Output Message above shows different number of Reads for both the queries when ran twice. Logical reads 148, physical reads 0, read-ahead reads 0,

Lob logical reads 0, lob physical reads 0, lob read-ahead reads 0. Logical reads 148, physical reads 0, read-ahead reads 148,

Run the following block of T-SQL statements: Let's Clear up the Data Cache or memory-buffer: SELECT BusinessEntityID, Title, FirstName, MiddleName, LastName, Suffix, EmailPromotion, ModifiedDate We will crate a new table here and populate records from AdventureWorks's Person.Person table:

#COUNT AND GROUP BY IN ADVENTUREWORKS2012 CODE#

вЂ“> LetвЂ™s go by some T-SQL Code examples to make it more simple to understand: These are a kind of advance Physical Reads, as they bring the Pages in advance to the Data Cache where the need for Data/Index pages in anticipated by the query. вЂ“ Read-Ahead Reads: are the number of 8k Pages pre-read from the Disk and placed into the Data Cache. Once in Data Cache they (Pages) are read by Logical Reads and Physical Reads do not (or minimally) happen for same set of queries. вЂ“ Physical Reads: are the Number of 8k Pages read from the Disk if they are not in Data Cache.

These Pages are placed in Data Cache by Physical Reads or Read-Ahead Reads. вЂ“ Logical Reads: are the number of 8k Pages read from the Data Cache. Here in this post I will go ahead and talk about Page Reads, i.e Logical Reads and Physical Reads. In my previous post I talked about SET STATISTICS IO and Scan Count.

Count and group by in adventureworks2012