Getting a SQL Server RowCount Without doing a Table Scan
By: Andy Novick | Comments (2) | Related: More > TSQL
Sometimes there is a need to get record counts from every table in your database. One way of doing this is to do a SELECT count(*) on all of your tables, but this could create a lot of overhead especially for large databases and large tables. If you don't require an exact answer, it isn't necessary to use a SELECT count(*) query on the rows in a table to get the row count.
Thanks to Andrew Novick at Novick Software here is the answer. SQL Server keeps the row count in sysindexes and it can be retrieved there. The key is to select the correct record from sysindexes. Sysindexes is a system table that exists in every database.
SQL Server maintains at least one row in sysindexes for every user table. A few of the most important columns are:
|id||int||ID of the table referred to by this row|
|indid||int||See the text that follows...|
|rowcnt||bigint||Number of rows in the index|
The indid column tells us what part of the table structure this row of sysindexes is referring to:
|0||Table data when there is no clustered index|
|1||Refers to the clustered index|
|2 - 254||Non-clustered indexes|
|255||Text or Image data pages|
A table will only have an entry in sysindexes with an indid value of for 0 or 1, never both. That's the entry that we're interested in because its rowcnt field gives us the number of rows in the table. Here is a query that shows the table, index and indid from the pubs database:
SELECT so.[name] as [table name]
, CASE WHEN si.indid between 1 and 254
THEN si.[name] ELSE NULL END
AS [Index Name]
FROM sysindexes si
INNER JOIN sysobjects so
ON si.id = so.id
WHERE si.indid < 2
AND so.type = 'U' -- Only User Tables
AND so.[name] != 'dtproperties'
ORDER BY so.[name]
Here are the results:
|table name||Index Name||indid|
As you can see from the results, most of the indexes are clustered (indid=1) but a few tables such as discounts don't have a clustered index (indid=0).
I started this tip with "If you don't need an exact answer..." That's because there are times when rowcnt is not the exact number of records in the table.
This can be corrected by updating statistics on the table with:
Here's the CREATE FUNCTION script for udf_Tbl_RowCOUNT
|CREATE FUNCTION dbo.udf_Tbl_RowCOUNT (|
@sTableName sysname -- Table to retrieve Row Count
RETURNS INT -- Row count of the table, NULL if not found.
* Returns the row count for a table by examining sysindexes.
* This function must be run in the same database as the table.
* Common Usage:
SELECT dbo.udf_Tbl_RowCOUNT ('
PRINT 'Test 1 Bad table ' + CASE WHEN SELECT
dbo.udf_Tbl_RowCOUNT ('foobar') is NULL
THEN 'Worked' ELSE 'Error' END
* © Copyright 2002 Andrew Novick http://www.NovickSoftware.com
* You may use this function in any of your SQL Server databases
* including databases that you sell, so long as they contain
* other unrelated database objects. You may not publish this
* UDF either in print or electronically.
DECLARE @nRowCount INT -- the rows
DECLARE @nObjectID int -- Object ID
SET @nObjectID = OBJECT_ID(@sTableName)
-- Object might not be found
IF @nObjectID is null RETURN NULL
SELECT TOP 1 @nRowCount = rows
WHERE id = @nObjectID AND indid < 2
GRANT EXECUTE ON [dbo].[udf_Tbl_RowCOUNT] TO PUBLIC
Let's use it:
|use pubs -- assuming the UDF was created in pubs|
, dbo.udf_Tbl_RowCOUNT ([name]) as [Row Count]
WHERE type='U' and name != 'dtproperties'
ORDER BY [name]
Here are the results:
- Add this User Defined Function to your database toolkit
- Continue to learn more about the system tables and how they can help you manage your SQL Servers
- Check out Novick Software for some other great UDFs and SQL Server Tips
- Take a look at Andrew Novick's book Transact-SQL User-Defined Functions for some great UDFs all in one resource
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