>I have an IBOQuery with an SQL containing a LEFT JOIN :
>
>SELECT
> CAST(:USAGER_ AS VARCHAR(10)) AS USAGER,
> TCSELECT.XS,
> TCCLIENTS.ID_CLIENT,
> TCCLIENTS.CLIENT,
> TCCLIENTS.NOMCLIENT,
> TCCLIENTS.ASSOCIE,
> TCCLIENTS.ENTITE,
> TCCLIENTS.GROUPE,
> TCCLIENTS.GROUPE2,
> TCCLIENTS.RESP,
> TCCLIENTS.REVISEUR,
> TCCLIENTS.FINANNEE
>FROM
> TCCLIENTS
> LEFT JOIN TCSELECT ON (TCCLIENTS.CLIENT = TCSELECT.CLIENT AND TCSELECT.USAGER = :USAGER_)
>
>Though, when a filter is applied, like
>WHERE ((UPPER( TCCLIENTS.ASSOCIE ) = 'AP'))
>
>All the data from the TCSELECT.XS is lost. When I show the data in a grid, the whole column gets blank. Only a manual RefreshRows will get the data back.
>
>I've tried putting the join conditions in the Joi nLinks of the DataSet. This correctly displayed the 'XS' field when a filter was applied,
>though it corrupted the dataset SQL when further filters were applied (as expected).
>
>How to automatically get the right 'XS' column value when a filter is applied?

Don't think of parameters as variables. To Firebird, your two references to :USAGER_ are two different parameters. IBO tries to make it so that you can treat them as if they were a variable, but I wouldn't be surprised if it failed in somewhat odd cases like yours. I was bitten by this some time ago when I tried to use the same parameter against one CHAR and one VARCHAR field (I think that has since been corrected in IBO, but I learnt that I should never think of parameters as variables).

If you have only one reference to the parameter, the query (and filter) may work (unless the reason for your error is different from what I believe). So try something like this:

with tmp(USAGER) as
(SELECT CAST(:USAGER_ AS VARCHAR(10)
FROM RDB$DATABASE)
SELECT
tmp.USAGER,
TCSELECT.XS,
TCCLIENTS.ID_CLIENT,
TCCLIENTS.CLIENT,
TCCLIENTS.NOMCLIENT,
TCCLIENTS.ASSOCIE,
TCCLIENTS.ENTITE,
TCCLIENTS.GROUPE,
TCCLIENTS.GROUPE2,
TCCLIENTS.RESP,
TCCLIENTS.REVISEUR,
TCCLIENTS.FINANNEE
FROM
TCCLIENTS
CROSS JOIN tmp
LEFT JOIN TCSELECT ON TCCLIENTS.CLIENT = TCSELECT.CLIENT AND TCSELECT.USAGER = tmp.USAGER

HTH,
Set