SQL从所有选定的行中减去第一行

Question

有没有办法从所有行中减去第一个选定行的值？所以,如果我有

t = 1, v = 500
t = 2, v = 800
t = 3, v = 1200

我会的

t = 1, v = 0
t = 2, v = 300
t = 3, v = 700

我一直在寻找便携式解决方案,但Postgres解决方案的工作原理相同:-)谢谢.

Answer 1

SELECT  v - FIRST_VALUE(v) OVER (ORDER BY t)
FROM    mytable
ORDER BY
        t