Вземете членове на семейството

Решението, което намерих, не е никак добро. Той дава правилния отговор, но е много бавен, дори за тази много малка таблица.

 DECLARE @INCLUIDOS TABLE (ID INT)

 INSERT INTO @INCLUIDOS VALUES(1)

 DECLARE @PAST_QUANT INT = 0
 DECLARE @QUANT INT = 1 

 WHILE @QUANT <> @PAST_QUANT
 BEGIN

     SET @PAST_QUANT = @QUANT

     INSERT INTO @INCLUIDOS
        SELECT PARENT 
        FROM PERSONCONN 
        WHERE CHILD IN (SELECT ID FROM @INCLUIDOS)
            AND PARENT NOT IN (SELECT ID FROM @INCLUIDOS)

    INSERT INTO @INCLUIDOS
        SELECT CHILD
        FROM PERSONCONN
        WHERE PARENT IN (SELECT ID FROM @INCLUIDOS)
            AND CHILD NOT IN (SELECT ID FROM @INCLUIDOS)

    SET @QUANT = (SELECT COUNT(*) FROM @INCLUIDOS)

END

SELECT DISTINCT ID FROM @INCLUIDOS

SQL Fiddle