sql server - SQL subs select sometimes returning 2 values causing extra Rows -

i have sql statement following. right it's returning values both projectrate , rate. want return rate when rate >= 0 , not null. if that's not true want return project rate when project rate >= 0 , not null. if both null or both <0 want return 0. right it's returning rate , projectrate if both exist instead of picking rate on projectrate

and have tables joined correctly, used generic names keep simple

edit: here's full query

select distinct  ph.id_projecthours,  ph.status, ph.hoursquantity, ph.entrydate, ph.entryyear, ph.entrymonth, ph.entryweek, ph.entrydescription, ph.deliverablecode, ph.wbsline, ph.itemvalue, ph.itemdescription, ph.lastmodifieddate, ph.lastmodifieduser, ph.synergyrequestid, p.projectname, p.projectdescription, p.projectmanager, p.projectbudgettimemat, p.projectbudgetfixed, p.projectrate, p.projectbudget, p.projectcontingency, p.contingencytype, p.contingencyremaining, p.discount, p.golivedate, p.invoiceinstruction, e.employeename, e.fte, b.typename, bt.budgettypename, cc.costcentername, cc.costcenterdescription, cfu.cfuname, d.departmentname, c.customername, c.customersynergyid, i.internalrate, i.currency, i.startdate ratestart, i.enddate rateend, (select(coalesce(case when per.rate > 0 rate else null end, case when p.projectrate > 0 p.projectrate else null end, 0))) calcrate  dbo.projecthours ph     inner join dbo.project p         on p.id_project = ph.id_project     inner join dbo.employee e         on e.id_employee = ph.id_employee     inner join dbo.billabletype b         on b.id_billabletype = ph.id_billabletype     inner join dbo.budgettype bt         on p.id_budgettype = bt.id_budgettype     inner join dbo.costcenter cc         on cc.id_costcenter = p.id_costcenter     inner join dbo.cfu         on cc.id_cfu = cfu.id_cfu     inner join dbo.department d         on cfu.id_department = d.id_department     inner join dbo.customer c         on c.id_customer = p.id_customer     left join dbo.internal         on i.id_employee = e.id_employee , i.internalrate <> 0 ,  ph.entrydate between i.startdate , i.enddate      left join dbo.projectemployeerates per         on per.id_employee = e.id_employee  

try case statement this:

    case         when rate >= 0 rate        when projectrate >= 0 projectrate        else 0     end