SQL SERVER How to deleting big volume of data from very huge table

Issue

We one of very huge database which running out of server disk space. I was asked to remove millions of historical data from some huge table. When I try to run DELETE with where condition directly, I got two problems. Firstly, whole table blocked for long time (long then 12 hours). Secondly, after run DELETE the ldf Database log file increased exponentially and the script ending with error because disk is full.

Solution

Base on the server’s situation, we may using different way to solve this issue.

1. We just want to Deleting All the data from the table then the best option will be Truncate table directly, as below:

TRUNCATE TABLE huge_history_table


This TRUNCATE TABLE command will remove all rows from a table, without logging the individual row deletions. TRUNCATE TABLE is similar to the DELETE statement with no WHERE clause; however, TRUNCATE TABLE is faster and uses fewer system and transaction log resources.

2. We want to deleting more than 80-90 Percent of the data from the huge table and this table can be offline for short period. We can using SELECT INTO script to move the data (data need to keep) to another staging table. Then Truncate this Large table and Insert back the staging data. as below:

SELECT * INTO staging_table
FROM huge_table
WHERE create_date>’DateAdd(month, -1, Convert(datetime, GetDate()))’


TRUNCATE TABLE huge_table


INSERT INTO huge_table (column_name)
SELECT column_name
FROM staging_table

3. One last option I can think of is to change your database’s Recovery Mode to SIMPLE and then delete rows in smaller batches using a while loop something like this. We want to delete large historical data from the table, the table need to be accessed by system 24×7 and cannot find a time take if offline. Then we delete rows in smaller batches using a while loop something as below:

DECLARE @Deleted_Rows INT;
SET @Deleted_Rows = 1;

WHILE (@Deleted_Rows > 0)
BEGIN
— Delete some small number of rows at a time
DELETE TOP (10000) LargeTable
WHERE create_date<‘DateAdd(month, -1, Convert(datetime, GetDate()))’

SET @Deleted_Rows = @@ROWCOUNT;
END

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