'FG1 - FlexGrid с данными вида "Таблица.Поле"
'Есть массив ArrTbl где хранятся имена выбранных таблиц.
Dim ln As Integer
Dim str As String
Dim a As String
Dim b As String
FG1.Row =  0 
FG1.Col =  1 
s = "SELECT "
Do While FG1.Text <> ""
    str = str & FG1.Text & ","
    FG1.Col = FG1.Col +  1 
Loop

s = s & str
ln = Len(s) -  1 
a = Mid(s,  1 , ln) & " FROM "
i =  1 
s = ""
Do While ArrTbl(i) <> ""
    s = s & ArrTbl(i) & ","
    i = i +  1 
Loop

ln = Len(s) -  1 
b = Mid(s,  1 , ln)
a = a & b & ";"

SELECT Табл1.Поле1, Табл2.Поле2, Табл1.Поле3 FROM Табл1, Табл2;

'FG1 - FlexGrid с данными вида "Таблица.Поле"
'Есть массив ArrTbl где хранятся имена выбранных таблиц.
'a - итоговый запрос

Dim ArrKey( 1  To  100 ,  1  To  2 ) As String
Dim ArrKeyTbl( 1  To  100 ,  1  To  2 ) As String
Dim ArrKeyTbl2( 1  To  100 ) As Boolean
Dim KeyCnt As Integer
Dim ArrKeyClk( 1  To  100 ) As String

Dim KeyRS As ADODB.Recordset
Dim KeyRS2 As ADODB.Recordset
Set KeyRS = New ADODB.Recordset
Set KeyRS2 = New ADODB.Recordset

KeyRS.ActiveConnection = cn
KeyRS2.ActiveConnection = cn
sqlKeys = "SELECT FK.TABLE_NAME+'.'+FK.COLUMN_NAME , PK.TABLE_NAME+'.'+PK.COLUMN_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE PK JOIN 
INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C ON 
PK.CONSTRAINT_CATALOG=C.UNIQUE_CONSTRAINT_CATALOG AND 
PK.CONSTRAINT_SCHEMA=C.UNIQUE_CONSTRAINT_SCHEMA AND 
PK.CONSTRAINT_NAME=C.UNIQUE_CONSTRAINT_NAME JOIN 
INFORMATION_SCHEMA.KEY_COLUMN_USAGE FK ON 
C.CONSTRAINT_CATALOG=PK.CONSTRAINT_CATALOG AND 
C.CONSTRAINT_SCHEMA=FK.CONSTRAINT_SCHEMA AND C.CONSTRAINT_NAME=FK.CONSTRAINT_NAME 
AND PK.ORDINAL_POSITION=FK.ORDINAL_POSITION ORDER BY 
FK.CONSTRAINT_NAME,PK.ORDINAL_POSITION;"

sqlKeys2 = "SELECT FK.TABLE_NAME, PK.TABLE_NAME FROM 
INFORMATION_SCHEMA.KEY_COLUMN_USAGE PK JOIN 
INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C ON 
PK.CONSTRAINT_CATALOG=C.UNIQUE_CONSTRAINT_CATALOG AND 
PK.CONSTRAINT_SCHEMA=C.UNIQUE_CONSTRAINT_SCHEMA AND 
PK.CONSTRAINT_NAME=C.UNIQUE_CONSTRAINT_NAME JOIN 
INFORMATION_SCHEMA.KEY_COLUMN_USAGE FK ON 
C.CONSTRAINT_CATALOG=PK.CONSTRAINT_CATALOG AND 
C.CONSTRAINT_SCHEMA=FK.CONSTRAINT_SCHEMA AND C.CONSTRAINT_NAME=FK.CONSTRAINT_NAME
 AND PK.ORDINAL_POSITION=FK.ORDINAL_POSITION ORDER BY 
FK.CONSTRAINT_NAME,PK.ORDINAL_POSITION;"

KeyRS.Open sqlKeys
KeyRS2.Open sqlKeys2


i =  1 
Do While Not KeyRS.EOF
ArrKey(i,  1 ) = KeyRS.Fields( 0 ) 'имена полей FK
ArrKey(i,  2 ) = KeyRS.Fields( 1 ) 'имена полей PK
ArrKeyTbl(i,  1 ) = KeyRS2.Fields( 0 ) 'тоже самое но только имена таблиц
ArrKeyTbl(i,  2 ) = KeyRS2.Fields( 1 )
KeyRS.MoveNext
KeyRS2.MoveNext
i = i +  1 
Loop
KeyRS.Close
KeyCnt = i -  1 

Dim ln As Integer
Dim str As String
Dim a As String
Dim b As String

ClkCnt =  1 
FG1.Row =  0 
FG1.Col =  1 
s = "SELECT "

Do While FG1.Text <> "" 'собираем имена полей
    str = str & FG1.Text & ", " 
    FG1.Col = FG1.Col +  1 
Loop

s = s & str
ln = Len(s) -  2  'избавляемся от лишней запятой
a = Mid(s,  1 , ln) & " FROM "

i =  1 
s = ""
Tcnt =  1 
Do While ArrTbl(i) <> "" 'собираем имена таблиц 
    s = s & ArrTbl(i) & ", "
    i = i +  1 
Loop

ln = Len(s) -  2  'избавляемся от лишней запятой
b = Mid(s,  1 , ln)
a = a & b

Tcnt = i -  1 

For i =  1  To Tcnt   'сравниваем выбранные пользователем таблицы со связанными
    For j =  1  To Tcnt
        For i1 =  1  To KeyCnt
                If (ArrTbl(i) = ArrKeyTbl(i1,  2 )) And (ArrTbl(j) = ArrKeyTbl(i1,  1 )) Then
                    ArrKeyTbl2(i1) = True
                End If
        Next i1
    Next j
Next i

ClkCnt =  1 
For i =  1  To KeyCnt  'собираем связанные поля
    If ArrKeyTbl2(i) Then
        ArrKeyClk(ClkCnt) = ArrKey(i,  1 ) & " = " & ArrKey(i,  2 )
        ClkCnt = ClkCnt +  1 
    End If
Next i

If ArrKeyClk( 1 ) <> "" Then   'проверяем, были ли среди выбранных таблиц взязанные
    s = " WHERE "
    For i =  1  To ClkCnt
        s = s & ArrKeyClk(i) & " and "
    Next i
    ln = Len(s) -  10  'избавляемся от лишних ANDов
    b = Mid(s,  1 , ln)
    a = a & b
End If

a = a & ";"
'запрос готов
MsgBox a