How do I handle NULL or empty varchar values that cause the conversion error?

Before attempting the conversion, check for NULL or empty varchar values. You can use `IS NULL` or `LEN(varchar_column) = 0` in your SQL query to identify these cases. Use `CASE` statements to handle them appropriately, either by providing a default datetime value or excluding them from the conversion process. For example: `CASE WHEN varchar_column IS NULL OR LEN(varchar_column) = 0 THEN NULL ELSE CONVERT(datetime, varchar_column, 120) END`.