Question

1- what is the performance difference of below commands?

 ... Where ID in (1,2,3)


... where ID = 1 OR ID = 2 OR ID = 3

2- where is performance difference of below commands(condition priority)?

... where Condition1 and condition2  ->  ... where condition2 and condition1
... where Condition1 OR condition2  ->  ... where condition2 OR condition1

Answer 1

There is no difference between the below two type; since anyways, at runtime your DB engine will flatten the IN clause to an OR’d stack. So IN(1,2,3) will get expanded to col = 1 OR col = 2 OR col = 3

... Where ID in (1,2,3)   

... where ID = 1 OR ID = 2 OR ID = 3