Problem with use of variable form fields

[DSMejantel]

Hi,
I want to build a form to check if pupils are presents or not.
I use the example of forms with a variable number of fields
It's work fine.
But if I want to edit and delete pupils or if nobody is present, the base is correctly modified but I can go to the returning clause because JSON_EACH(sqlpage.variables('post')) is empty.

I stay on a white page !

How can i do ?

--Insertion dans la base
DELETE FROM livret where prestation_id=$prestation and classe_id=$classe_select

INSERT INTO livret(prestation_id, jour, service_id, classe_id, tarif, present, eleve_id, parent_id) 
SELECT
    $prestation as prestation_id,
    (SELECT strftime('%m/%Y',jour) FROM prestation WHERE id=$prestation) as jour,   
    (SELECT service_id FROM prestation WHERE id=$prestation) as service_id,
    $classe_select as classe_id,
    (SELECT tarif from prestation WHERE prestation.id=$prestation) as tarif,
    CAST(value AS INTEGER)as present,
    CAST(key AS INTEGER) as eleve_id,
    (SELECT parent_id FROM eleves WHERE eleves.id=CAST(key AS INTEGER)) as parent_id
FROM JSON_EACH(sqlpage.variables('post'))

 RETURNING 
     'redirect' AS component,
    '/saisie_tableau.sql?prestation='||$prestation AS link;

[lovasoa]

You don't need the returning anyway ! RETURNING is useful when you need autogenerated values from the rows you just inserted. In your case, just use a plain select.

INSERT [...] FROM JSON_EACH(sqlpage.variables('post'));

 SELECT 
     'redirect' AS component,
    '/saisie_tableau.sql?prestation='||$prestation AS link;

[DSMejantel]

Thanks !