How to improve the performance of the query and what is the Use of "Instead of Caluse"??

Hi ,

I have small doubts on performance tunning and "Instead of Caluse" i.e.

1)at what time we need to apply tunning for the queires ?

2) If we use hints then how the performance will increase, what is the realtion to hints and perfomance.?

3) Is it really decrease the performance if we hard code the value in where condition?

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Why we should use "Instead of " while updating complex views. pls expain in detail?

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what are different types of Optimizers and explain plz ?

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Thanks,