Hash join vs nested loop

Question

DECLARE @tableA table (Productid varchar(20),Product varchar(20),RateID int)
insert into @tableA values('1','Mobile',2);
insert into @tableA values('2','Chargers',4);
insert into @tableA values('3','Stand',6);
insert into @tableA values('4','Adapter',8);
insert into @tableA values('5','Cover',10);
insert into @tableA values('6','Protector',12);
--SELECT * FROM @tableA
DECLARE @tableB table (id varchar(20),RateID int,Rate int)
insert into @tableB values('1',2,200);
insert into @tableB values('2',4,40);
insert into @tableB values('3',6,60);
insert into @tableB values('4',8,80);
insert into @tableB values('5',10,10);
insert into @tableB values('6',12,15);
--SELECT * FROM @tableB
SELECT Product,Rate
FROM @tableA a
JOIN @tableB b ON a.RateID = b.RateID
Above is the sample query, where in execution plan it shows the Hash Match (inner Join). Now how do I change it to Nested Loop with out changing the query? help plz

Answer 1

Is Hash Match(inner join) or Nested loop is better to have in the query?
That depends on the size of the tables, available indexes etc. The optimizer will (hopefully) make the best choice.
Above is the sample query, where in execution plan it shows the Hash Match (inner Join). Now how do I change it to Nested Loop with out changing the query?
The answer that you should leave that to the optimizer in most cases.
I see that the logical read for nested loop is higher than Hash Match.
But Hash Match tends to need more CPU. The best way to two compare two queries or plans is wallclock time.
On a big tables, how do we reduce the logical read? 
Make sure that there are usable indexes.
Erland Sommarskog, SQL Server MVP, [email protected]