I am new to MS ADO and trying to understand how to set the size on command parameters as created by the

command.CreateParameter (Name, Type, Direction, Size, Value)

The documentation says the following:

Size
Optional. A Long value that specifies the maximum length for the parameter value in characters or bytes.

...

If you specify a variable-length data type in the Type argument, you must either pass a Size argument or set the Size property of the Parameter object before appending it to the Parameters collection; otherwise, an error occurs.

1.) What should one pass for fixed-size parameters? Is it a "don't care"?

I was a bit confused by the example found here, in which they set size to 3 for an adInteger parameter with Value set to a variant of type VT_I2

pPrmByRoyalty->Type = adInteger;
pPrmByRoyalty->Size = 3;
pPrmByRoyalty->Direction = adParamInput;
pPrmByRoyalty->Value = vtroyal;

VT_I2 implies two bytes. A tagVARIANT struct is 16 bytes. How did they land on three? I see that the enum value for adInteger happens to be three, but I suspect that is just a coincidence.

So it's a bit confusing what to pass for fixed-size parameters. The team I'm working with has always passed sizeof(int) for adInteger, and it seems to work. Is that correct?

Now, for "variable-length" parameters: we are instructed by the documentation to pass "the maximum length .. in characters or bytes".

2.) For adVarChar, is it sufficient to pass the max width as defined in the database?

3.) What about the Wide types (e.g. adVarWChar)? Is it characters or bytes?

4.) How about adVariant, which could contain fixed- or variable-length data?

5.) Do arrays ever come into play here? (we don't pass them as parameters, just curious)

Any references or personal insights are welcome.