$1.$ What is SQL performance tuning?

$2.$ What is the focus of most performance tuning activities, and why does that focus exist?

$3.$ How are database statistics obtained?

$4.$ If indexes are so important, why not index every column in every table? $($Include a brief

discussion of the role played by data sparsity$).$

$5.$ Most query optimization techniques are designed to make the optimizer$$s work easier.

What factors should you keep in mind if you intend to write conditional expressions in

SQL code?

$6.$ What does RAID stand for, and what are some commonly used RAID levels?