Question

MS Access allows the numeric type GUID (in German it’s called ‘Replikations-ID’, so I guess in English that would be ‘replication id’) which is stored as a 16 byte binary field in the database.

I found how to access these fields in Delphi with TADOQuery/TADOTable using

(TheQuery.FieldByName('SomeGuidField') as TGUIDField).AsGuid; 

But now I want to execute an SQL-Query like this:

SELECT * FROM SomeTable WHERE SomeGuidField=:AGuid 

I tried setting a TADOQuery.SQL property to the above statement, but found no way to actually set the AGuid parameter such that the query can be opened. Whatever I tried resulted in the (ADO/COM) error

No value given for one or more required parameters

For example:

TheQuery.ParamByName('AGuid').Value := QuotedString(GuidToStr(AGuid)); TheQuery.Open; // <<== crashes here 

This doesn’t work either:

TheQuery.ParamByName('AGuid').Value := GuidToStr(AGuid); TheQuery.Open; // <<== crashes here 

I had a look at how TGuidField(...).AsGuid works and found that it first converts the GUID to a string and then the string to a variant (and vice versa).

It works fine, if I always generate the SQL-Statement like this:

SELECT * FROM SomeTable WHERE SomeGuidField='<a guid goes here>' 

As I am passing that TADOQuery object around in the program I would like to only change the AGuid-Parameter to keep most methods agnostic on the actual SQL-Statement.

Is there any other way to set a GUID-Parameter than always change the complete SQL-Statement?

(It must be a GUID because I need a globally unique identifier to synchronize with other databases which are MS SQL or MS Access based.)

Edit vradmilovic is right, this works:

TheQuery.ParamByName('AGuid').Value := GuidToStr(AGuid); TheQuery.Open; 

I don’t understand why it didn’t work the first time I tried it.

Answer 1

That’s correct way to set parameters with ADO. The message you get is most probably due to typo with some of fields (you get same message if field does not exist).