is the expaination correct?

Question

is the explaination of given question correct?

Explanation:

Result of inner query is non empty because even no record satisfy where condition of inner query count(*) produces 1 record.

So, every record of R  where condition true

My question: how count getting 1 record?

Comments

No count=0 and count= NULL are both different.

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@ Pankaj Joshi 

what that 1 means, when count return 0?

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1 tupple  
where count value is 0 in that tupple