joins-nested loops,hash or merge

[malay_biswal]

1. It depends on how big are the tables. If tables are small or it's using FIRST_ROWS chances are more it'll use nested loop.
2. I would suggest to rad some basic indexing material. They affect query performance drastically.

3. Go through this.
http://www.dba-oracle.com/t_table_join_order.htm

first of all thanks for dat link.It helped me get the basics right.
I still have few doubts:
1. Do the indexes on both joined key columns affect the type of join to be used?
---I've indexed both columns but still it is nested loops..Will it go on to use sort merge
join with larger data set?

2.How do indexes affect query's performance?

3. How does the join order affect query's performance?