How many tuples are returned by SQL Query

Question

Consider the following relation instance myTable

num1	num2
100	100
100	NULL
NULL	100
NULL	NULL

 

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Query 1:

SELECT *

FROM myTable

WHERE num1 = 100;

Query 2:

SELECT *

FROM myTable

WHERE num1 <> 100;

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If Query 1 returns p tuples and Query 2 returns q tuples, then 10p+q will be  _____________

Answer 1

20 as null comparing with anything will result in false.

Answer 2

20??

Comments

yes 20,If the predicate evaluates to either false or unknown for a tuple in R1×· · ·×Rn
(the projection of) the tuple is not added to the result.

Answer 3

p=2 and q=0

10*p+q = 20

Answer is 20

Answer 4

The first query returns 2 tuples so p = 2 and the second query returns 0 tuples because num1 <> 100 doesn’t return the row which has num1 value as NULL because we can’t compare the NULL values like this it results in  unknown so q = 0,

so final answer we get is 20.