Question

I have several tables in a database. One table (tbl_transactions) has thousands of orphaned records that are not linked to any of the remaining tables. I need to run a script that will delete these records in order to regain some lost space in my database. I tried to run a script that deleted all the records, but the log file consumed 20 GB of space, thus filling the HDD and the script did not complete. My script looks like this:

delete tbl_Transactions
where not exists (select * 
                    From tbl_SocketConnections
                   where tbl_Transactions.TransactionID = tbl_SocketConnections.TransactionID)
  And Not Exists(Select * 
                   From tbl_ProtocolCommands
                  where tbl_Transactions.TransactionID = tbl_ProtocolCommands.TransactionID)
  And Not Exists(Select * 
                   From tbl_EventRules
                  where tbl_Transactions.TransactionID = tbl_EventRules.TransactionID)

There are several other tables, but the pattern repeats. Can someone advise on how I can limit the scope of this script to say 1000 records at a time?

Answer 1

SQL Server 2005+

Change TOP to LIMIT covers mySQL too

SELECT 'starting' --gives one row
WHILE @@ROWCOUNT <> 0
    delete TOP (10000) tbl_Transactions
    where not exists (select * 
                        From tbl_SocketConnections
                       where tbl_Transactions.TransactionID = tbl_SocketConnections.TransactionID)
      And Not Exists(Select * 
                       From tbl_ProtocolCommands
                      where tbl_Transactions.TransactionID = tbl_ProtocolCommands.TransactionID)
      And Not Exists(Select * 
                       From tbl_EventRules
                      where tbl_Transactions.TransactionID = tbl_EventRules.TransactionID)