SELECT T1.Room, T1.Symbol As Symbol1, T2.Symbol As Symbol2, T3.Symbol As Symbol3
FROM (tbl1 As T1 INNER JOIN tbl1 As T2 ON T1.Room=T2.Room And T1.Symbol<T2.Symbol) 
INNER JOIN tbl1 As T3 ON T2.Room=T3.Room And T2.Symbol<T3.Symbol
ORDER BY T1.Room, T1.Symbol, T2.Symbol, T3.Symbol

SELECT Room, Mid(Symbol3, num,1) As Symbol FROM
(SELECT num FROM tabTri) As Q1,
(SELECT TOP 100 PERCENT T1.Room, T1.Symbol & T2.Symbol & T3.Symbol As Symbol3
FROM (tbl1 As T1 INNER JOIN tbl1 As T2 ON T1.Room=T2.Room And T1.Symbol<T2.Symbol) 
INNER JOIN tbl1 As T3 ON T2.Room=T3.Room And T2.Symbol<T3.Symbol
ORDER BY T1.Room,T1.Symbol & T2.Symbol & T3.Symbol) As Q2

SELECT Room, Mid(Symbol3, num1, InStr(num1, Symbol3, "|")-num1) AS Symbol
FROM (SELECT (D2.digit & D1.digit & D0.digit)+1 AS num, num+1 As num1
      FROM Digits AS D0, Digits AS D1, Digits AS D2) AS Q1, 
     (SELECT T1.Room, "|" & T1.Symbol & "|" & T2.Symbol & "|" & T3.Symbol & "|" As Symbol3
      FROM (tbl1 As T1 INNER JOIN tbl1 As T2 ON T1.Room=T2.Room And T1.Symbol<T2.Symbol) 
      INNER JOIN tbl1 As T3 ON T2.Room=T3.Room And T2.Symbol<T3.Symbol) AS Q2
WHERE num<Len(Symbol3) And Mid(Symbol3, num,1)="|"
ORDER BY Room, Symbol3, num

SELECT Q2.Room, Switch( ... ) AS Выражение1
FROM tabTri, (SELECT T1.Room, T1.Symbol &'*' &T2.Symbol &'|'& T3.Symbol AS Symbol3 
FROM (tbl1 AS T1 INNER JOIN tbl1 AS T2 ON (T1.Symbol<T2.Symbol) AND (T1.Room=T2.Room)) 
INNER JOIN tbl1 AS T3 ON (T2.Symbol<T3.Symbol) AND (T2.Room=T3.Room)) AS Q2
ORDER BY Room, Symbol3, num