Question

I have come across articles that state that SELECT COUNT(*) FROM TABLE_NAME will be slow when the table has lots of rows and lots of columns.

I have a table that might contain even billions of rows [it has approximately 15 columns]. Is there a better way to get the EXACT count of the number of rows of a table?

Please consider the following before your answer:

• I am looking for a database vendor
  independent solution. It is OK if it
  covers MySQL, Oracle, MS SQL Server.
  But if there is really no database
  vendor independent solution then I
  will settle for different solutions
  for different database vendors.

• I cannot use any other external tool
  to do this. I am mainly looking for a
  SQL based solution.

• I cannot normalize my database design
  any further. It is already in 3NF and moreover a
  lot of code has already been written
  around it.

Answer 1

Simple answer:

• Database vendor independent solution = use the standard = COUNT(*)
• There are approximate SQL Server solutions but don’t use COUNT(*) = out of scope

Notes:

COUNT(1) = COUNT(*) = COUNT(PrimaryKey) just in case

Edit:

SQL Server example (1.4 billion rows, 12 columns)

SELECT COUNT(*) FROM MyBigtable WITH (NOLOCK)
-- NOLOCK here is for me only to let me test for this answer: no more, no less

1 runs, 5:46 minutes, count = 1,401,659,700

--Note, sp_spaceused uses this DMV
SELECT
   Total_Rows= SUM(st.row_count)
FROM
   sys.dm_db_partition_stats st
WHERE
    object_name(object_id) = 'MyBigtable' AND (index_id < 2)

2 runs, both under 1 second, count = 1,401,659,670

The second one has less rows = wrong. Would be the same or more depending on writes (deletes are done out of hours here)