Empty select result when dates are used

Initial data: have a paragraph of query which in the sake of reasoning can be simplified to next

SELECT MAX((CASE 
          WHEN to_char(sy开发者_如何学Pythonsdate, 'DY') = 'SAT' THEN 1 
          WHEN to_char(sysdate, 'DY') = 'SUN' THEN 1
          ELSE 0 END)) status 
FROM mytable WHERE mycondition;

The problem: it appears that if mycondition results in empty result set first two when conditions don't work as they should and return null instead of 1. If I simply substitute the last line of query with next

FROM dual;

first two when conditions work flawless.

Condition: It should only be a query, no ifs, var defs etc.

How is it possible to perform this type of select but without a null value returned?

P.S.: Can use NVL/NVL2 but that really complicates the thing.

Thanks in advance.

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Use a NVL function:

SELECT NVL(MAX((CASE 
          WHEN to_char(sysdate, 'DY') = 'SAT' THEN 1 
          WHEN to_char(sysdate, 'DY') = 'SUN' THEN 1
          ELSE 0 END)), 1) status 
FROM mytable WHERE mycondition;

---

CASE WHEN works fine, your problem is with MAX.

MAX and MIN return null when no rows match while SUM and COUNT return 0.

I'm afraid den-javamaniac is right, you need NVL, or perhaps a smart use of DECODE if you cannot switch out MAX.