Use vertical splitting if:
Some columns are accessed more frequently than other columns.
The table has wide rows, and splitting the table reduces the number of pages that need to be read.
Vertical table splitting makes even more sense when both of the above conditions are true. When a table contains very long columns that are accessed infrequently, placing them in a separate table can greatly speed the retrieval of the more frequently used columns. With shorter rows, more data rows fit on a data page, so for many queries, fewer pages can be accessed.