> How I can speed up it?

> SELECT
>   ID,
>   DENOMINAZIONE,
>   SCADENZA,
>   PARTITA,
>   NUMERO_DOCUMENTO,
>   DATA_DOCUMENTO,
>   IMPORTO,
>   IMPORTO - PAGATO AS RESIDUO,
>   PAGATO,
>   PAGAMENTO,
>   SALDARE
> from
> (
> SELECT
>   C.ID,
>   C.DENOMINAZIONE,
>   PNS.SCADENZA,
>   PNS.PARTITA,
>   PNT.NUMERO_DOCUMENTO,
>   PNT.DATA_DOCUMENTO,
>   PNS.IMPORTO,
>   COALESCE((SELECT
>                          SUM(PNC2.AVERE - PNC2.DARE)
>                        from
>                          PN_CORPO PNC2
>                        WHERE
>                          PNC2.PARTITA = PNS.PARTITA
>                          AND PNC2.SCADENZA = PNS.SCADENZA

<SL> Create an index on PN_CORPO( PARITA, SCADENZA)

>                          AND PNC2.SCADENZA IS NOT NULL
>                       ), 0) AS PAGATO,
>   0.00 AS PAGAMENTO,
>   '0' AS SALDARE
> from
>   PN_SCADENZE PNS,
>   PN_CORPO PNC,
>   CLIENTI C,
>   PN_TESTA PNT
> where
>   PNS.PN_TESTA_ID = PNC.PN_TESTA_ID
>   AND C.ID = PNC.CLIENTE_ID
>   AND PNT.ID = PNS.PN_TESTA_ID

<SL> Use modern SQL syntax for JOINs:

From PN_SCADENZE PNS,
JOIN PN_CORPO PNC ON PNC.PN_TESTA_ID = PNS.PN_TESTA_ID
JOIN CLIENTI C ON C.ID = PNC.CLIENTE_ID
JOIN PN_TESTA PNT = PNT.ID = PNS.PN_TESTA_ID

> )
>
> From Statistics of Flamerobin:
>
> Prepare time: 0.014s
> PLAN (PNC2
> NATURAL) PLAN JOIN (PNC NATURAL, PNT INDEX (PN_TESTA_PK), C INDEX
> (PK_CLIENTI), PNS INDEX (PN_SCADENZE_FK))
>
> Executing...
> Done.
> 4684158 fetches, 0 marks, 0 reads, 0 writes.
> 0 inserts, 0 updates, 0 deletes, 3011 index, 2313903 seq.
> Delta memory: 70560 bytes.
> Total execution time: 1.608s
> Script execution finished
>
> The time 1.608s if referred at only 300 rows fetched as defaults of
> flamerobin. In production I have 1157 rows affected (they grows rapidly) in
> near 6.20s.