Oracle PL/SQL/Data Type/NULL

2 meaningless values can"t be compared against one another

 
SQL> select 12 from dual where null = null;
no rows selected
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This in the only way to do it properly to get the desired results

 
SQL> select 12 from dual where null is null;
        12
----------
        12
1 row selected.
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using the nvl function

 
SQL> select 12 from dual where nvl(null,"X") = nvl(null,"X");
        12
----------
        12
1 row selected.
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