如何在使用sql查询获取日期的最新记录时，在同一列中减去两行的值？

SELECT 
    date_column,
    value_column,
    ROW_NUMBER() OVER (ORDER BY date_column DESC) AS row_num
FROM 
    your_table

SELECT 
    t1.date_column,
    t1.value_column - t2.value_column AS difference
FROM 
    (
        SELECT 
            date_column,
            value_column,
            ROW_NUMBER() OVER (ORDER BY date_column DESC) AS row_num
        FROM 
            your_table
    ) t1
    JOIN (
        SELECT 
            date_column,
            value_column,
            ROW_NUMBER() OVER (ORDER BY date_column DESC) AS row_num
        FROM 
            your_table
    ) t2 ON t1.row_num = t2.row_num + 2