Oracle not evaluating nvl as expected

Question

This query returns rows where colA is null:

select * from viewA where colA is null;

But this query does not -

select * from viewA where nvl(colA, 'X') = 'X';

Any idea why the second query is not returning any results?

Answer 1

从viewA选择*其中nvl（colA，'null'）='null';