This script will delete rows within a table that are out-with the specified retention period. This can be useful if you’re running deletes on large tables, and particularly if;
#– Deletes are taking a long time & you’re finding it difficult to track progress.
#– You have a short maintenance window each day to perform such tasks, which could be due to caution over blocking/deadlocks.
#– Your server is not equipped to handle the log file bloat associated with running the delete as a single transaction.
Whatever the reason is, this is a useful script to have in the toolbelt.
I’ve set this to delete 10k rows at a time, although you can find your own sweet spot.
SET NOCOUNT ON
DECLARE @today_floored DATETIME, @retention_period INT, @retention_date DATETIME
-- Get today, clearing time to 12:00am
SET @today_floored = (SELECT DATEADD(m, DATEDIFF(m, 0, GETDATE()), 0)) --+(SELECT [rollover_time] FROM [table])
-- Set retention period (in months, unless the line above is changed)
SET @retention_period = 13
-- Apply retention date deduction to floored date
SELECT @retention_date = DATEADD(m, -@retention_period, @today_floored)
PRINT 'Deleting data < '+ CAST(@retention_date AS VARCHAR(20))
-- Delete in batches; set preferred rowcount and enter the table/column names
DECLARE @BatchSize INT = 1, @total BIGINT = 0
SET rowcount 10000
WHILE @BatchSize <> 0
WHERE [ShipDate] < @retention_date
SET @BatchSize = @@rowcount
SET @total = @total + @batchsize
To find out how long it’ll take until all rows have been deleted, you could do something like;
a. Get row counts.
b. Run deletion script for 10 minutes.
c. Check how many rows were affected.
d. Refresh Disk Usage by Top Tables report / get new counts.
e. Compare numbers above.
f. If the math works out to be 9 months before it’ll finish, then get an index added.