SQL Server - Return all records from LEFT table and only non matching records from right table

Question

I have 2 tables with the same structure (field names). Table1 and Table2.

I need to return all records from Table1 and only records from Table2 that do not match/join to a record in Table1.

Table2 has more records than Table1.

I am joining the 2 tables on 3 fields.

So basically I want all records from table1 returned and only records that don't have a match (joining on the 3 fields) to table1 from table2 returned.

Put another way, Table1 records take precedence over table2 records in my final result output when the records exist in both tables (same value for the 3 fields)

I started writing something like the below but I don't think it will work. Should I use a left outer join instead?

    Select * from table1 t1
    left join table2 t2 on t1.id = t2.id and t1.date = t2.date and t1.custid= t2.custid
where t2.id is null or t2.date is null or t2.custid is null

Answer 1

So, you need every row from table1 plus the rows from table2 that don't match with table1 ?:

SELECT *
FROM table1
UNION ALL
SELECT *
FROM table2 t2
WHERE NOT EXISTS(SELECT * FROM table1
                 WHERE id = t2.id
                 AND date = t2.date
                 AND custid = t2.custid);

Answer 2

Select * from table1 t1
  Union
Select * from table2 t2
Where Not exists
     (Select * from table1 
      Where id = t1.id 
         and date = t1.date 
         and custid= t1.custid)