No of rows

Question

Answer 1

Here ans will be (c)1

inner query first executed i.e. select manager from emp ; and this fetches 2,3,4

Now, outer query will be executed and the rows of eno.=2 or 3 or 4 will not be prined

So, it only prints

eno           ename            manager

  1                 a                         2

Comments

According to ans key : 

is It correct!!!

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I don't think that key is correct. You can try on a DBMS..

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yes, I think NULL cannot make any change here.

Answer 2

ans d is correct....whenever not in operator compare with null value condition become false....so no row is selected...