SQL - Sumar columnas que tengan dos campos iguales en SQL

SELECT Fecha, SUM(Monto) as Total

FROM  RegistrosVentas

group by Fecha

drop table #Tmp

Create Table #Tmp(

Fecha_Hora smalldatetime,

No_Comprobante int,

No_Linea smallint,

Lote int,

Pcb smallint,

Pedido smallint,

Ingreso smallint,

Egreso smallint,

Saldo smallint

)

go

Insert into #Tmp values('2005-05-02 01:15:00',4,1,21,6,334,167,0,0)

Insert into #Tmp values('2005-05-03 15:07:10',5,1,29,6,167,167,0,0)

Insert into #Tmp values('2005-07-01 12:25:15',6,1,12,6,200,50,0,0)

Insert into #Tmp values('2005-07-01 21:05:52',25,1,1,6,200,0,140,0)

Insert into #Tmp values('2005-07-02 21:05:52',25,1,1,6,200,9,0,0)

Insert into #Tmp values('2005-07-03 21:05:52',25,1,1,6,200,0,140,0)

Insert into #Tmp values('2005-07-04 21:05:52',25,1,1,6,200,100,0,0)

Insert into #Tmp values('2005-07-05 21:05:52',25,1,1,6,200,0,150,0)

Insert into #Tmp values('2005-07-06 21:05:52',25,1,1,6,200,20,0,0)

Insert into #Tmp values('2005-07-07 21:05:52',25,1,1,6,200,0,20,0)

Insert into #Tmp values('2005-07-08 21:05:52',25,1,1,6,200,100,0,0)

Insert into #Tmp values('2005-07-09 21:05:52',25,1,1,6,200,0,20,0)

go

select

        a.fecha_hora,

        a.ingreso,

        a.egreso,

        sum(b.ingreso - b.egreso) as saldo

from

        #Tmp as a

        inner join

        #Tmp as b

        on b.Fecha_Hora <= a.Fecha_Hora

group by

        a.fecha_hora,

        a.ingreso,

        a.egreso

order by

        1 asc

go

drop table tmp

go

Si este calculo lo quieres hacer por producto, entonces debes agregar una

condicion mas al "inner join", que es:

a.product_id = b.productid