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15 Jul 2010 1:24 PM
Recently, I’ve been involved in a very interesting project in which we need to perform operations on a table containing 3,000,000,000+ rows. For some tooling, I needed a quick and reliable way to count the number of rows contained within this table. Performing a simple
SELECT COUNT(*) FROM Transactions
operation would do the trick on small tables with low IO, but what’s the ‘best’ way (quick and reliable) to perform this operation on large tables?
I searched and found different answers, which I note here so it might be of use to someone… (My table was called ‘Transactions’)
| Index | Query | Comment |
| 1 | SELECT COUNT(*) FROM Transactions | Performs a full table scan. Slow on large tables. |
| 2 | SELECT CONVERT(bigint, rows)
FROM sysindexes WHERE id = OBJECT_ID(‘Transactions’) AND indid < 2 |
Fast way to retrieve row count. Depends on statistics and is inaccurate.
Run DBCC UPDATEUSAGE(Database) WITH COUNT_ROWS, which can take significant time for large tables. |
| 3 | SELECT CAST(p.rows AS float)
FROM sys.tables AS tbl INNER JOIN sys.indexes AS idx ON idx.object_id = tbl.object_id and idx.index_id < 2 INNER JOIN sys.partitions AS p ON p.object_id=CAST(tbl.object_id AS int) AND p.index_id=idx.index_id WHERE ((tbl.name=N’Transactions’ AND SCHEMA_NAME(tbl.schema_id)=’dbo’)) |
The way the SQL management studio counts rows (look at table properties, storage, row count). Very fast, but still an approximate number of rows. |
| 4 | SELECT SUM (row_count)
FROM sys.dm_db_partition_stats WHERE object_id=OBJECT_ID(‘Transactions’) AND (index_id=0 or index_id=1); |
Quick (although not as fast as method 2) operation and equally important, reliable. |