SQL - Ayuda con consulta

cliente |factura|concepto|vencimiento |importe
------------------------------------------------
juan |0000001|cuota  |10-01-2009 |10
juan |0000001|impuesto|10-01-2009 |2
juan |0000001|extras  |10-01-2009 |3
juan |0000002|cuota  |10-02-2009 |10
juan |0000002|impuesto|10-02-2009 |2
juan |0000003|cuota  |10-03-2009 |10
juan |0000003|impuesto|10-03-2009 |2
juan |0000003|extras  |10-03-2009 |3

cliente |deuda |facturas adeudadas
-----------------------------------
juan |42 |3

SELECT CLIENTE, Sum(IMPORTE) AS DEUDA, Count(CONCEPTO) AS FACTURAS_ADEUDADAS
FROM DEUDAS
WHERE CONCEPTO = 'CUOTA'
GROUP BY CLIENTE

 
cliente |deuda |facturas adeudadas
-----------------------------------
juan |30 |3

 
SELECT CLIENTE, Sum(IMPORTE) AS DEUDA, Count(CONCEPTO) AS FACTURAS_ADEUDADAS
FROM DEUDAS
GROUP BY CLIENTE

 
cliente |deuda |facturas adeudadas
-----------------------------------
juan |42 |8

SELECT cliente, SUM(importe) AS deuda, COUNT(*) AS cantidad
FROM (SELECT cliente, factura, SUM(importe)
      FROM deudas
      GROUP BY cliente, factura) AS por_factura
GROUP BY cliente

 
SELECT a.CLIENTE, Sum(a.IMPORTE) AS DEUDA, 
(select count(b.CONCEPTO) from deudas b 
where b.cliente=a.cliente and b.concepto='CUOTA') AS TOTAL_CUOTAS
FROM DEUDAS a
GROUP BY a.CLIENTE

SELECT cliente, SUM(importe), SUM(DECODE(concepto, 'cuota', 1, 0))
FROM deudas
GROUP BY cliente