Can this be done in SQL? - I can do it in JAVA - Calculate Waitlists

I am developing some hardcoded rep开发者_开发技巧orts from embedded Java code to Crystal Reports

there is a function that calculates "waitlists"

My Datamodel is as follows (I've left out all of the columns and tables that are not relevant)

Each table is denoted as with * and the columns are denoted with a + their relationships are

Person table 1 to * Sessions table 1 to * Outcomes table

*Person table   
    +id - primary key


*Sessions table   
    +parentid  foreign key to Person.id
    +id   - primary key
    +isValid  
    +session-name

*Outcomes table
    +parentid  foreign key to Sessions.id
    +id -primary key
    +session-name

The logic is as follows ( i need this in sql(MSSQL preferred)):

Count the number of occurrences of each outcome that complies with the following

get a list of unique outcomes for each person and for each of those outcomes

if there is no session with the same name as that-outcome & is valid & also has the same parent id as that-outcome's parent session

I hope that makes sense : any help is appreciated

Something like that:

SELECT
    p.id           AS personID
  , s.id           AS sessionID
  , s.session-name AS sessionName
  , o.id           AS outcomeID
  , o.session-name AS outcomeSessionName
FROM Person AS p
  JOIN Sessions AS s
    ON s.parentid = p.id
  JOIN Outcomes AS o
    ON o.parentid = s.id
WHERE NOT EXISTS
      ( SELECT *
        FROM Sessions AS s2
        WHERE s2.session-name = o.session-name
          AND s2.isValid
          AND s2.parentid = s.parentid
      )

If you also want to count these outcomes, it would be more complex query. Perhaps it's better to have another query, that counts what you want (all outcomes? per person?)