Question

humbly I ask for help with the next problem.

I have this one very simple. Don’t know how to describe it by words so I’ll do with an image.

table services

PERSONID     Service_id          chargeamount
1               3                 20.50
2               4                 80.50
3               5                 78.80

table charges

service_id     payed          extracharges
3               true              20.50
4               true              80.50
3               false             78.80

if there is any unpayed extracharge it must show true or false , and if the service id do not match in the second table it must be shown in the query with null values or other calculated value

Something like this

PERSONID     Service_id          chargeamount                        payed
1               3                 20.50                              false
2               4                 80.50                              true
3               5                 78.80                              null

but extra rows of the same row are not allowed like the ones created by joins.

SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[SERVICES](
    [personid] [int] NULL,
    [service_id] [int] NULL,
    [chargeamount] [float] NULL
) ON [PRIMARY]

GO


insert into services (personid,service_id,chargeamount) values ( 1,3  ,20);
insert into services (personid,service_id,chargeamount) values ( 2,4  ,20);
insert into services (personid,service_id,chargeamount) values ( 3,5 ,20);



SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[charges](
    [payed] [bit] NULL,
    [service_id] [int] NULL,
    [extracharges] [float] NULL
) ON [PRIMARY]

GO

insert into services (service_id,payed,extracharges) values ( 3,true,20.50);
insert into services (service_id,payed,extracharges) values ( 3,false,78.80);
insert into services (service_id,payed,extracharges) values ( 4,false,80.50);

Answer 1

This is a simple left join on service_id. When there is at least one row with payed = false, false is shown. Otherwise true or null is shown, respectively.

select s.*, case min(c.payed) when 1 then 'true' when 0 then 'false' else 'null' end
from services s
left join charges c on c.service_id = s.service_id
group by s.personid, s.service_id, s.chargeamount

SQLFiddle