Poblem with Query to Get Diference

I am using this query to show Saldo column With Invoices and Payments Values. Works Good but if i dont have an invoice but i have a payment, i can see It until i add an invoice. How can i correct It?

select B.razonsocial as Empresa, Facturas , 
IFNULL(pay,0) as Pagos, (Facturas - IFNULL(pay,0)) Saldo 
FROM (select TblFacturasCompras.id_proveedor, TblProveedores.razonsocial, 
SUM(case when TblFacturasCompras.tipocomprobante = 'A' or TblFacturasCompras.tipocomprobante='B' or TblFacturasCompras.tipocomprobante = 'NDA' or TblFacturasCompras.tipocomprobante = 'NDB'  or TblFacturasCompras.tipocomprobante = 'C'  or TblFacturasCompras.tipocomprobante = 'NDC' or TblFacturasCompras.tipocomprobante = 'X' then TblFacturasCompras.total else -TblFacturasCompras.total end)  as Facturas 
from TblFacturasCompras left join TblProveedores on TblFacturasCompras.id_proveedor = TblProveedores.id group by TblProveedores.id) A 
LEFT JOIN (select TblProveedores.id, TblProveedores.razonsocial, SUM(TblRecibosCompras.total) as Pay from 
TblProveedores left join TblRecibosCompras on TblRecibosCompras.id_proveedor = TblProveedores.id  group by TblProveedores.id) B ON A.id_proveedor = B.id 
where B.razonsocial <> '' order by B.razonsocial Asc

Solution

you are using a column involved in left join in a where condition

 where B.razonsocial <> ''

this work as an inner join try add the condition to the related on clause

select B.razonsocial as Empresa
    , Facturas
    , IFNULL(pay,0) as Pagos
    , (Facturas - IFNULL(pay,0)) Saldo 
    FROM (  
        select TblFacturasCompras.id_proveedor
            , TblProveedores.razonsocial
            , SUM(case when 
                        TblFacturasCompras.tipocomprobante = 'A' 
                        or TblFacturasCompras.tipocomprobante='B' 
                        or TblFacturasCompras.tipocomprobante = 'NDA' 
                        or TblFacturasCompras.tipocomprobante = 'NDB'  
                        or TblFacturasCompras.tipocomprobante = 'C'  
                        or TblFacturasCompras.tipocomprobante = 'NDC' 
                        or TblFacturasCompras.tipocomprobante = 'X' 
                    then TblFacturasCompras.total 
                    else -TblFacturasCompras.total end)  as Facturas 
        from TblFacturasCompras 
        left join TblProveedores on TblFacturasCompras.id_proveedor = TblProveedores.id 
        group by TblProveedores.id
    ) A 
    LEFT JOIN (
        select TblProveedores.id
            , TblProveedores.razonsocial
            , SUM(TblRecibosCompras.total) as Pay 
        from TblProveedores 
        left join TblRecibosCompras on TblRecibosCompras.id_proveedor = TblProveedores.id  
        group by TblProveedores.id
    ) B ON A.id_proveedor = B.id and  B.razonsocial <> '' 
    order by B.razonsocial Asc

and a suggestion you could use a IN clause instead of several OR clause

select B.razonsocial as Empresa
    , Facturas
    , IFNULL(pay,0) as Pagos
    , (Facturas - IFNULL(pay,0)) Saldo 
    FROM (  
        select TblFacturasCompras.id_proveedor
            , TblProveedores.razonsocial
            , SUM(case when 
                  TblFacturasCompras.tipocomprobante IN ('A','B','NDA','NDB','C','NDC','X') 
                    then TblFacturasCompras.total 
                    else -TblFacturasCompras.total end)  as Facturas 
        from TblFacturasCompras 
        left join TblProveedores on TblFacturasCompras.id_proveedor = TblProveedores.id 
        group by TblProveedores.id
    ) A 
    LEFT JOIN (
        select TblProveedores.id
            , TblProveedores.razonsocial
            , SUM(TblRecibosCompras.total) as Pay 
        from TblProveedores 
        left join TblRecibosCompras on TblRecibosCompras.id_proveedor = TblProveedores.id  
        group by TblProveedores.id
    ) B ON A.id_proveedor = B.id and  B.razonsocial <> '' 
    order by B.razonsocial Asc