Table-valued function displaying only 1 result - sql-server

Question

I've got this table valued function and I want it to display all records with the same "PeopleID". How can I do it? It's currently displaying only 1 of the possible results.
ALTER FUNCTION dbo.ufnGetContactInformation(#FuncID int)
RETURNS #retContactInformation TABLE
(
-- Columns returned by the function
FuncID int PRIMARY KEY NOT NULL,
Full_Name nvarchar(75) NULL,
Phone nvarchar(100) NULL,
Email nvarchar(50) NULL,
City nvarchar(20) NULL
)
AS
BEGIN
DECLARE
#fullname nvarchar(75),
#phonenumber nvarchar(100),
#email nvarchar(50),
#city nvarchar(20);
-- > Get common contact information
SELECT
#fullname = p.Full_Name,
#phonenumber = c.Phone,
#email = c.Email,
#city = c.CityID
FROM d_People p, d_Contacts c
WHERE p.PeopleID=#FuncID;
-- < Get common contact information
IF #FuncID IS NOT NULL
BEGIN
INSERT #retContactInformation
SELECT #FuncID, #fullname, #phonenumber, #email, #city;
END;
RETURN;
END;
GO

Answer 1

You need a proper join for your two tables, otherwise your query makes no sense. What you have now will give you one person full_name, but every contact phone, email, and city.
Bad habits to kick : using old-style JOINs - Aaron Bertrand
When you select into the scalar variables, you will only get one result in each variable. Inserting the variables after setting them to only hold one row will only ever yield at most one row.
You can simplify your function as an in-line table-valued function like so:
alter function dbo.ufngetcontactinformation(#funcid int)
returns table as return (
select
funcid = p.peopleid
, fullname = p.full_name
, phonenumber = c.phone
, email = c.email
, city = c.cityid
from d_people p, d_contacts c
where p.peopleid = #funcid;
);
go
Reference
When is a SQL function not a function? "If it’s not inline, it’s rubbish." - Rob Farley
Inline Scalar Functions - Itzik Ben-Gan
Scalar functions, inlining, and performance: An entertaining title for a boring post - Adam Machanic
TSQL User-Defined Functions: Ten Questions You Were Too Shy To Ask - Robert Sheldon
If you have to have a multi-statement table valued function despite the perfomance hit:
alter function dbo.ufngetcontactinformation(#funcid int)
returns #retcontactinformation table
(
-- columns returned by the function
funcid int primary key not null,
full_name nvarchar(75) null,
phone nvarchar(100) null,
email nvarchar(50) null,
city nvarchar(20) null
)
as
begin
insert #retcontactinformation
select
#funcid
, p.full_name
, c.phone
, c.email
, c.cityid
from d_people p, d_contacts c
where p.peopleid = #funcid;
return;
end;
go