Execute T-SQL Batches in a Loop

In T-SQL, the keyword “GO” is the default batch separator.

For example:

DELETE

FROM

    ErrorLog

WHERE

    ErrorTime < ’2008-01-01′

GO

But what if you have billions of rows in the “ErrorLog” table and you need to delete them a batch at a time so that you don’t lock up the entire table? You can use the “TOP” operator to specify the batch size and then specify an integer value that follows the “GO” keyword specifying the number of batches to execute.

For example:

DELETE
TOP(100000)

FROM

    ErrorLog

WHERE

    ErrorTime < ’2008-01-01′

GO 10000

In this example, we specify the batch size to 100,000 by using the “TOP” operator and then we specify the number of times to execute this batch by specifying 10,000 after the “GO” keyword. This block of code will now execute 10,000 times each time deleting 100,000 records from the “ErrorLog” table.

Specifying the batch count after the “GO” keyword is a very powerful yet frequently overlooked tool available to you in SQL Server 2005 & 2008. It allows you to specify a single number to execute a block of code in a loop without setting up counters and BEGIN / END blocks for simple blocks of code. This is a great addition to anyone’s SQL toolkit.