Original:        Expected:

Key   Value         Key    Value
A     #foo          A      #foo, #bar
A     #bar          B      #foo, #bar, #foobar
B     #foo
B     #bar
B     #foobar

  
DEFINE FILE MY_TABLE
     NEW_VALUE/A300V = IF KEY EQ LAST KEY THEN (NEW_VALUE || (', ' | VALUE)) ELSE VALUE;
END

APP PREPENDPATH IBISAMP
TABLE FILE CAR
PRINT COMPUTE LIST/I5= IF COUNTRY EQ LAST COUNTRY THEN LAST LIST + 1 ELSE 1;
BY COUNTRY
BY CAR
ON TABLE HOLD AS CAR1
END
TABLE FILE CAR1
WRITE CAR
BY COUNTRY
ACROSS LIST NOPRINT
END

APP PREPENDPATH IBISAMP

TABLE FILE CAR
LIST CAR
BY COUNTRY
BY CAR
ON TABLE HOLD AS CAR1
END

DEFINE FILE CAR1
CAR_LIST/A200V=IF LIST EQ 1 THEN CAR ELSE (LAST CAR_LIST) || (', ' | CAR);
END


TABLE FILE CAR1
WRITE LST.CAR_LIST AS 'CARS'
BY COUNTRY
END

TABLE FILE MY_TABLE
   SUM COMPUTE NEWVALUE/A1000V = IF LAST KEY EQ KEY THEN NEWVALUE | ',' | VALUE ELSE VALUE;
   BY  KEY
END

TABLE FILE IBISAMP/CAR
   SUM COMPUTE NEWVALUE/A1000V = IF LAST COUNTRY EQ COUNTRY THEN NEWVALUE | ',' | CAR ELSE CAR;
   BY  COUNTRY
END

TABLE FILE CAR
PRINT COMPUTE NEWVALUE/A1000V = IF LAST COUNTRY EQ COUNTRY THEN NEWVALUE | ',' | CAR ELSE CAR; 
   BY  COUNTRY
BY TOTAL HIGHEST 1 NEWVALUE NOPRINT
END

TABLE FILE CAR
PRINT COMPUTE NEWVALUE/A1000V = IF LAST COUNTRY EQ COUNTRY THEN NEWVALUE | ',' | CAR ELSE CAR; 
BY  COUNTRY
BY TOTAL HIGHEST 1 NEWVALUE NOPRINT
END

TABLE FILE CAR
BY  COUNTRY
BY TOTAL HIGHEST 1 COMPUTE NEWVALUE/A1000V = IF LAST COUNTRY EQ COUNTRY THEN NEWVALUE | ',' | CAR ELSE CAR; 
END

TABLE FILE CAR
PRINT CAR NOPRINT
BY  COUNTRY
BY TOTAL HIGHEST 1 COMPUTE NEWVALUE/A1000V = IF LAST COUNTRY EQ COUNTRY THEN NEWVALUE | ',' | CAR ELSE CAR; 
END

  
TABLE FILE filename
LIST Value
BY Key
ON TABLE HOLD
END
TABLE FILE HOLD
SUM Value
BY Key
ACROSS LIST NOPRINT
END