if condition, then upsert else do nothing - sql

Question

I am trying to upsert a value only if a condition is true, otherwise I dont want to do anything to the record. My code seems to generate primary key errors when I run it again (indicating the insert is firing, but the whole statement should be skipped)
Error on second run: Violation of PRIMARY KEY constraint 'PK__chicken__A2D9E564407C90CD'. Cannot insert duplicate key in object 'dbo.chicken'. The duplicate key value is (10118-78843).
Query:
IF((select status from chicken where [PrimaryKey]='10118-78843')!='paid')
update [eComm]..[chicken] set [Status]='Overdue' where [PrimaryKey]='10118-78843'
IF ##ROWCOUNT=0 insert into [eComm]..[chicken]([PrimaryKey],[Status]) values('10118-78843','Paid');
create example table code:
create table chicken(
PrimaryKey nvarchar(50) not null,
Status nvarchar(10),
PRIMARY KEY (PrimaryKey)
)
Goal (this is invalid syntax):
IF((select status from chicken where [PrimaryKey]='10118-78843')!='paid')
{
update [eComm]..[chicken] set [Status]='Overdue' where [PrimaryKey]='10118-78843'
IF ##ROWCOUNT=0 insert into [eComm]..[chicken]([PrimaryKey],[Status]) values('10118-78843','Paid');
}
else, do nothing

Answer 1

The problem is that you are not taking into account what happens if there is an existing row but the status is paid.
You need to tweak the logic a bit:
declare #status varchar(20) = (
select c.status
from chicken c
where c.[PrimaryKey] = '10118-78843'
);
if (#status != 'paid')
update [chicken]
set [Status] = 'Overdue'
where [PrimaryKey] = '10118-78843';
else if (#status is null)
insert into [chicken] ([PrimaryKey], [Status])
values ('10118-78843', 'Paid');
Alternatively:
insert into [chicken] ([PrimaryKey], [Status])
select '10118-78843', 'Paid'
where not exists (select 1
from chicken c
where c.[PrimaryKey] = '10118-78843'
);
if (##ROWCOUNT = 0)
update [chicken]
set [Status] = 'Overdue'
where [PrimaryKey] = '10118-78843'
and status != 'Paid';