HEELPBOOK - SQL Server - Alternative way to get the table's row count #################

To get the total row count in a table, we usually use the following select statement:


SELECT count(*) FROM table_name


This query performs full table scan to get the row count.

You can check it by setting SET SHOWPLAN ON for SQL Server 6.5 or SET SHOWPLAN_TEXT ON for SQL Server 7.0/2000. 
So, if the table is very big, it can take a lot of time. 

In this example, the tbTest table will be created and 10000 rows will be inserted into this table:


CREATE TABLE tbTest (
  id int identity primary key,
  Name char(10)
)
GO
DECLARE @i int
SELECT @i = 1
WHILE @i <= 10000
  BEGIN
    INSERT INTO tbTest VALUES (LTRIM(str(@i)))
    SELECT @i = @i + 1
  END
GO


There is another way to determine the total row count in a table. You can use the sysindexes system table for this purpose. 
There is ROWS column in the sysindexes table. 

This column contains the total row count for each table in your database. So, you can use the following select statement instead of above one:


SELECT rows FROM sysindexes WHERE id = OBJECT_ID('table_name') AND indid < 2


There are physical read and logical read operations. A logical read occurs if the page is currently in the cache. 
If the page is not currently in the cache, a physical read is performed to read the page into the cache. 
To see how many logical or physical read operations were made, you can use SET STATISTICS IO ON command.

This is the example:


SET STATISTICS IO ON
GO
SELECT count(*) FROM tbTest
GO
SELECT rows FROM sysindexes WHERE id = OBJECT_ID('tbTest') AND indid < 2
GO
SET STATISTICS IO OFF
GO


This is the result:


-----------
10000

(1 row(s) affected)

Table 'tbTest'. Scan count 1, logical reads 32, physical reads 0, read-ahead reads 0.
rows
-----------
10000

(1 row(s) affected)

Table 'sysindexes'. Scan count 1, logical reads 2, physical reads 0, read-ahead reads 0.



So, you can improve the speed of the first query in several times. 

This works for SQL Server 6.5 and SQL Server 7.0/2000/2005 as well.


############ ARTICLE INFO #############

Article Month: March
Article Date: 19/03/2012
Permalink: http://heelpbook.altervista.org/2012/sql-server-alternative-way-to-get-the-tables-row-count/
Source: http://www.mssqlcity.com/Articles/KnowHow/RowCount.htm
Language: English

View more articles on: http://www.heelpbook.net/
Follow us on Facebook: http://it-it.facebook.com/pages/HeelpBook/100790870008832
Follow us on Twitter: https://twitter.com/#!/HeelpBook
Follow us on RSS Feed: http://feeds.feedburner.com/Heelpbook