The following sample shows how to achieve this: –
EXEC
sp_rename ‘table_name.original_field_name’, ‘temp_field_name’, ‘COLUMN’go
ALTER TABLE [table_name] ADD [original_field_name] VARCHAR(1000)
go
UPDATE [table_name] SET [original_field_name] = SUBSTRING([temp_field_name], 1, 1000)
go
ALTER TABLE [table_name] DROP COLUMN [temp_field_name]
go