SQL project state pipeline query - sql

Question

I am working with a database that includes a history table showing when projects have moved to the next state of development. Here is some example data.
dbo.history_table
| ProjectID | State | Timestamp |
| 1 | 1 | 2018-03-22 10:38:27.000 |
| 1 | 2 | 2018-03-23 10:22:56.000 |
| 1 | 3 | 2018-03-24 12:18:32.000 |
| 2 | 1 | 2018-03-24 11:01:17.000 |
| 1 | 4 | 2018-03-25 10:32:41.000 |
| 2 | 4 | 2018-03-26 12:39:03.000 |
There are a number of states that look something like this:
| State # | Description | Notes
| State 1 | Planning |
| State 2 | Pre-Production |
| State 3 | Production |
| State 4 | Post-Production |
| State 5 | Successful | Terminal state
| State 6 | Unsuccessful | Terminal state
| State 7 | Cancelled | Terminal state
These states are roughly sequential, but not quite, and not always. For instance, each project can only end in one of the three terminal states. Furthermore, although all projects begin in State 1, not all projects hit all states before terminating.
I need to write a query that looks at a particular state and shows the next state those records move to. The data I need from this query would look something like this:
Report: State 2 Pipeline
| Total: | 100 |
| Moved to State 3: | 50 |
| Moved to State 4: | 0 |
| Moved to State 5: | 25 |
| Moved to State 6: | 0 |
| Moved to State 7: | 25 |

Answer 1

This applies the LEAD logic to find the next row's state and utilizes GROUPING SETS to add the grand total:
with cte as
(
select
State,
lead(State)
over (partition by ProjectID
order by Timestamp) as nextState
from myTable
)
select
case when grouping(nextState) = 1 then 'Total' else nextState end,
count(*)
from cte
where State = 2
group by grouping sets ((nextState), ())
order by grouping(nextState) desc, nextState
But it will not return a row for states that don't exist as next state. You need to Left join this select to the table describing the existing states.