I have a constraint on a MyID Integer. When I use it in Delphi like IndexByName := MyID and use it in a loop.

mytable.IndexByName := MyID;
mytable.First;
While not mytable.EOF do
         begin
                 Label.Caption := mytable.FieldByName('MyID').AsString;
                 mytable.Next;
         end;

I get:

1000
1100
2000
1500
1300
2100

And all rows does not show.

Do I need to create a index for MyID or are my Constrain corrupted?

Thanks,
Kim

KimHJ


A constraint controls data being added to a table, not being retrieved from it. You may have a corrupted table so its worth trying a repir. If that doesn't cure it a bit more information would be useful - what is the constraint, what rows are not showing, when did you add the constraint (was there already data there that didn't match the constraint)


Roy Lambert

Roy Lambert wrote:

>>A constraint controls data being added to a table, not being retrieved from it. You may have a corrupted table so its worth trying a repir. If that doesn't cure it a bit more information would be useful - what is the constraint, what rows are not showing, when did you add the constraint (was there already data there that didn't match the constraint)<<


Roy,
The constrain is an Integer and it was added when I created the table. I did run the repair.
I added a new Index using the same column as the Constraint that is working.

I was just confused sine when you create a Constriant it shows under index in the ElevateDB Manager.

Thanks,
Kim

KimHJ


Can you post the table definition?


Roy Lambert

Kim,

<<I was just confused sine when you create a Constriant it shows under index in the ElevateDB Manager.>>

That is absolutely normal, when you define a constraint an index is automatically created because it's needed to enforce the constraint.
There is no point in creating a new index by yourself on the same column - it's a duplication.

--
Fernando Dias
[Team Elevate]

Fernando


>That is absolutely normal, when you define a constraint an index is automatically created because it's needed to enforce the constraint.
>There is no point in creating a new index by yourself on the same column - it's a duplication.

Almost right It depends on the type of constraint.

Primary Key, Foreign Key & Unique will all create an index - after all that's the only way they will work. Check constraints will not since they don't need one.

Re-reading the original post I've just noticed <<mytable.IndexByName := MyID;>> EDBTable doesn't have IndexByName so I assume a typo and it should be IndexName but simply setting the index should not prevent rows from showing which is why I want the table structure so I can play around a little.

Roy

Roy,

<<Almost right It depends on the type of constraint.>>

Right, but Check Constraints are out of this game because they don't change row filtering, they only play a role when inserting or altering rows.

--
Fernando Dias
[Team Elevate]

Fernando

>Right, but Check Constraints are out of this game because they don't change row filtering, they only play a role when inserting or altering rows.

Neither do the others unless a filter is set. There is no filter set in the example given  With the code shown I'm actually surprised that Kim can tell what's happening (I generally add lines to a memo) and I'm wondering if its down to gui refresh rather than database.

Roy

Roy Lambert wrote:

>>Re-reading the original post I've just noticed <<mytable.IndexByName := MyID;>> EDBTable doesn't have IndexByName so I assume a typo and it should be IndexName but simply setting the index should not prevent rows from showing which is why I want the table structure so I can play around a little.<<

Roy,
If i have a index with the Field MyID and call the index CustomerID, then in my Delphi code I can not use IndexByName := 'MyID'; ?

Maybe that is why I get Access violation sometimes?

Kim

KimHJ


I've just tried a couple of experiments, trying to assign a non existent index to IndexName

---------------------------
Debugger Exception Notification
---------------------------
Project MOA.exe raised exception class EEDBException with message 'ElevateDB Error #401 The index NoSuchIndex does not exist'.
---------------------------
Break   Continue   Help  
---------------------------


and invalid field names to IndexFieldNames

---------------------------
Debugger Exception Notification
---------------------------
Project MOA.exe raised exception class EDatabaseError with message 'Names: No index for fields 'NoSuchIndex''.
---------------------------
Break   Continue   Help  
---------------------------

I also tried to use IndexByName and the app won't compile


[DCC Error] Names.pas(197): E2003 Undeclared identifier: 'IndexByName'


Roy Lambert