Hello
I am using oracle 12.2.0.1 and I have following LAG syntax in my query -
readvalue - nvl(lag(readvalue) over (partition by c_id, d_id, e_id order by readtime),0) diff_readvalue,
But when I get my output for first record, I get
| 82357 | 1913.8 | 1913.8 | 08012015 18:01:00 |
| 82357 | 1917.7 | 3.9 | 08022015 18:02:00 |
| 82357 | 1919.3 | 1.6 | 08032015 18:03:00 |
| 82357 | 1920.6 | 1.3 | 08042015 18:03:00 |
but since first record is starting point, I need to get something like this -
| 82357 | 1913.8 | 0 | 08012015 18:01:00 |
| 82357 | 1917.7 | 3.9 | 08022015 18:02:00 |
| 82357 | 1919.3 | 1.6 | 08032015 18:03:00 |
| 82357 | 1920.6 | 1.3 | 08042015 18:03:00 |
How can I achieve this? Thanks for your help