. Access, Visual Basic (VBA) DAO. . , , Microsoft Excel Microsoft Project, , , . ActiveX;
, , , Const.
Visual Basic , , , . Visual Basic Visual Basic "Vb" , vbTileHorizontal. DAO "db" , dbRelationUnique, Access "", , AcDataTransferType.
, , . , , , . , , . .
, :
[_.][_.]_
_ .
_ , .
_ . .
. :
[Public|Private] Const _ [As ] =
_ ( , ); . , , .
Const :
, /:
Const conPi = 3.14159255358979 Public Const conPlanets As Integer = 9
Const conDate = #1/1/97#
:
Public Const conVersion = "08.10.A"
Const conName = "Access"
, :
Public Const conPi = 3.14, conPlanets = 9, conRussiaPop = 1.7E+08
(=) , , . : Const conPi2 = conPi * 2
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Variant
Variant . Variant Visual Basic . :
Dim VarVariant ' Variant
VarVariant = "20" ' VarVariant "20" ( ).
VarVariant = VarVariant + 77 ' VarVariant 97
VarVariant = "Access " & VarVariant ' VarVariant ' "Access 97" ()
Variant , , , , :
Variant , Variant , ;
& +.
Variant : Empty, Null, Nothing Error.
Empty. , - . Variant Empty , 0, ("") Null. Empty IsEmpty:
If IsEmpty(Z) Then Z = 0
Variant Empty, ; 0, .
Empty , Variant ( 0, Null). Variant Empty Empty.
Null. Variant : Null. Null . - Null :
, Null, Null. , Null, , "" ; Null, Null;
Null, Variant, Null, , Null, Null;
Null , Variant.
Null Null:
Z = Null
, Null Variant, IsNull:
If IsNull(X) And IsNull(Y) Then
Z = Null
Else
Z = 0
End If
Null , Variant, .
Null , , Null , .
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Error. Error Variant , , . , , . . Error CVErr .
CVErr , , . , , , . , , , . CVErr .
Nothing , .