I have a list of deliveries of each month and i want to know for each month how many months has passed since the last delivery for each client.
for example seeing client 1
| client | month | deliveries |
|---|---|---|
| 1. 1 | 202101 | 2 |
| 1. 1 | 202102 | 0 |
| 1. 1 | 202103 | 1 |
| 1. 1 | 202104 | 0 |
| 1. 1 | 202105 | 0 |
| 1. 1 | 202106 | 1 |
the output of what i expect is the following table
| client | analisys_month | months_since_last_delivery |
|---|---|---|
| 1. 1 | 202101. | 0 |
| 1. 1 | 202102. | 1 |
| 1. 1 | 202103. | 0 |
| 1. 1 | 202104. | 1 |
| 1. 1 | 202105. | 2 |
| 1. 1 | 202106. | 0 |
my question is to make 1 query that can solve the variable months_since_last_delivery for each one f 36 months of performances whitout making union for 36 different querys one for each month
