How to delete large data of table in SQL without log

Question

I have a large data table  There are 10 million records in this table   What is the best way for this query     Delete LargeTable where readTime  lt  dateadd MONTH -7 GETDATE

User · Answer

I was able to delete 19 million rows from my table of 21 million rows in matter of minutes  Here is my approach   If you have a auto-incrementing primary key on this table  then you can make use of this primary key    Get minimum value of primary key of the large table where readTime  lt  dateadd MONTH -7 GETDATE      Add index on readTime  if not already present  this index will anyway be deleted along with the table in step 3    Lets store it in a variable  min primary  Insert all the rows having primary key   min primary into a staging table  memory table if no  of rows is not large    Drop the large table  Recreate the table  Copy all the rows from staging table to main table  Drop the staging table

User · Answer

You can also use GO   how many times you want to execute the same query    DELETE TOP  10000    TARGETDATABASE   SCHEMA   TARGETTABLE   WHERE readTime  lt  dateadd MONTH -1 GETDATE     -- how many times you want the query to repeat GO 100

User · Answer

This variation of M Ali s is working fine for me  It deletes some  clears the log and repeats  I m watching the log grow  drop and start over   DECLARE  Deleted Rows INT  SET  Deleted Rows   1  WHILE   Deleted Rows  gt  0    BEGIN    -- Delete some small number of rows at a time     delete top  100000  from InstallLog where DateTime between  2014-12-01  and  2015-02-01      SET  Deleted Rows     ROWCOUNT      dbcc shrinkfile  MobiControlDB log 0 truncateonly   END

User · Answer

If i say without loop  i can use GOTO statement for delete large amount of records using sql server  exa    IsRepeat      DELETE TOP  10000      FROM  lt TableName gt      IF   ROWCOUNT  gt  0          GOTO IsRepeat   like this way you can delete large amount of data with smaller size of delete   let me know if requires more information

User · Answer

If you are Deleting All the rows in that table the simplest option is to Truncate table  something like   TRUNCATE TABLE LargeTable GO   Truncate table will simply empty  the table  you cannot use WHERE clause to limit the rows being deleted and no triggers will be fired   On the other hand if you are deleting more than 80-90 Percent of the data  say if you have total of 11 Million rows and you want to delete 10 million another way would be to Insert these 1 million rows  records you want to keep  to another staging table  Truncate this Large table and Insert back these 1 Million rows   Or if permissions views or other objects which has this large table as their underlying table doesnt get affected by dropping this table you can get these relatively small amount of the rows into another table drop this table and create another table with same schema and import these rows back into this ex-Large table  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    DECLARE  Deleted Rows INT  SET  Deleted Rows   1    WHILE   Deleted Rows  gt  0    BEGIN    -- Delete some small number of rows at a time      DELETE TOP  10000   LargeTable       WHERE readTime  lt  dateadd MONTH -7 GETDATE       SET  Deleted Rows     ROWCOUNT  END    and dont forget to change the Recovery mode back to full and I think you have to take a backup to make it fully affective  the change or recovery modes

User · Answer

You can delete small batches using a while loop  something like this   DELETE TOP  10000   LargeTable  WHERE readTime  lt  dateadd MONTH -7 GETDATE    WHILE   ROWCOUNT  gt  0 BEGIN     DELETE TOP  10000   LargeTable      WHERE readTime  lt  dateadd MONTH -7 GETDATE    END

User · Answer

m-ali answer is right but also keep in mind that logs could grow a lot if you don t commit the transaction after each chunk and perform a checkpoint  This is how I would do it and take this article http   sqlperformance com 2013 03 io-subsystem chunk-deletes as reference  with performance tests and graphs   DECLARE  Deleted Rows INT  SET  Deleted Rows   1    WHILE   Deleted Rows  gt  0    BEGIN     BEGIN TRANSACTION     -- Delete some small number of rows at a time      DELETE TOP  10000   LargeTable       WHERE readTime  lt  dateadd MONTH -7 GETDATE          SET  Deleted Rows     ROWCOUNT      COMMIT TRANSACTION    CHECKPOINT -- for simple recovery model END

User · Answer

If you are willing  and able  to implement partitioning  that is an effective technique for removing large quantities of data with little run-time overhead   Not cost-effective for a once-off exercise  though

User · Answer

Shorter syntax   select 1 WHILE    ROWCOUNT  gt  0  BEGIN   DELETE TOP  10000  LargeTable    WHERE readTime  lt  dateadd MONTH -7 GETDATE    END

User · Answer

Another use   SET ROWCOUNT 1000 -- Buffer  DECLARE  DATE AS DATETIME   dateadd MONTH -7 GETDATE     DELETE LargeTable  WHERE readTime  lt   DATE WHILE   ROWCOUNT  gt  0 BEGIN    DELETE LargeTable  WHERE readTime  lt   DATE END SET ROWCOUNT 0   Optional    If transaction log is enabled  disable transaction logs   ALTER DATABASE dbname SET RECOVERY SIMPLE

User · Answer

If you are using SQL server 2016 or higher and if your table is having partitions created based on column you are trying to delete for example Timestamp column   then you could use this new command to delete data by partitions   TRUNCATE TABLE WITH   PARTITIONS                  n         This will delete the data in selected partition s  only and should be the most efficient way to delete data from part of table since it will not create transaction logs and will be done just as fast as regular truncate but without having  all the data deleted from the table   Drawback is if your table is not setup with partition  then you need to go old school and delete the data with regular approach and then recreate the table with partitions so that you can do this in future  which is what I did  I added the partition creation and deletion into insertion procedure itself  I had table with 500 million rows so this was the only option to reduce deletion time   For more details refer to below links  https   docs microsoft com en-us sql t-sql statements truncate-table-transact-sql view sql-server-2017  SQL server 2016 Truncate table with partitions  Below is what I did first to delete the data before I could recreate the table with partitions with required data in it  This query will run for days during specified time window until the data is deleted    connect  lt  lt ServerName gt  gt  use  lt  lt DatabaseName gt  gt   SET NOCOUNT ON  DECLARE  Deleted Rows INT  DECLARE  loopnum INT  DECLARE  msg varchar 100   DECLARE  FlagDate datetime  SET  FlagDate    getdate   - 31  SET  Deleted Rows   1  SET  loopnum   1     while  getdate    lt  convert datetime  2018-11-08 14 00 00 000  120   BEGIN     RAISERROR   WAIT for START   0 1  WITH NOWAIT        WAITFOR DELAY  00 10 00  END   RAISERROR   STARTING PURGE   0 1  WITH NOWAIT     WHILE  1 1  BEGIN     WHILE   Deleted Rows  gt  0 AND  datepart hh  getdate      gt   12 AND datepart hh  getdate      lt   20   --  getdate    lt  convert datetime  2018-11-08 19 00 00 000  120          BEGIN        -- Delete some small number of rows at a time          DELETE TOP  500000   dbo  lt  lt table name gt  gt           WHERE timestamp column  lt  convert datetime   FlagDate 102           SET  Deleted Rows     ROWCOUNT           WAITFOR DELAY  00 00 01           select  msg    ROWCOUNT    convert varchar  Deleted Rows            set  loopnum    loopnum   1          if  loopnum  gt  1000              begin                   begin try                         DBCC SHRINKFILE  N  lt  lt databasename gt  gt  log    0  TRUNCATEONLY                          RAISERROR   msg  0 1  WITH NOWAIT                  end try                  begin catch                      RAISERROR   DBCC SHRINK   0 1  WITH NOWAIT                    end catch                  set  loopnum   1              end         END WAITFOR DELAY  00 10 00  END  select getdate

User · Answer

Francisco Goldenstein  just a minor correction  The COMMIT must be used after you set the variable  otherwise the WHILE will be executed just once   DECLARE  Deleted Rows INT  SET  Deleted Rows   1   WHILE   Deleted Rows  gt  0  BEGIN     BEGIN TRANSACTION      -- Delete some small number of rows at a time     DELETE TOP  10000   LargeTable      WHERE readTime  lt  dateadd MONTH -7 GETDATE         SET  Deleted Rows     ROWCOUNT       COMMIT TRANSACTION     CHECKPOINT -- for simple recovery model  END

[sql-server] How to delete large data of table in SQL without log?

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