To subtract dates in SQL effectively, you can utilize the built-in date functions provided by your SQL database system. For instance, in PostgreSQL, you can simply use the subtraction operator directly between two dates. The result will be an interval representing the difference. For example, the query `SELECT date1 – date2 AS difference FROM your_table;` will yield the interval as a result. If you want the result in a specific format like days or months, you can use the `EXTRACT()` function. For instance, `SELECT EXTRACT(DAY FROM (date1 – date2)) AS days_difference FROM your_table;` will provide the difference in days.

In SQL Server, the approach is slightly different since it requires the use of the `DATEDIFF()` function, which calculates the difference between two dates based on a specified date part (such as year, month, day, etc.). The syntax would look like this: `SELECT DATEDIFF(DAY, date2, date1) AS days_difference FROM your_table;`. This function returns an integer value, representing the number of seconds, minutes, hours, days, or any specified time unit between the two dates. By leveraging these functions appropriately, you can manipulate and calculate date differences efficiently in SQL.