How to Simulate SIGN Function

Puzzle of the day:

How to simulate the SIGN function in Oracle SQL by only using CEIL, FLOOR, and ABS Oracle SQL functions along with arithmetic operators? No PL/SQL.

Solution:

SIGN(x)=CEIL(x/(1+ABS(x)))+FLOOR(x/(1+ABS(x)))

In SQL, we can demonstrate it as follows:

WITH r AS (
SELECT dbms_random.VALUE(-999,999) rnd
FROM dual
CONNECT BY LEVEL<=10
UNION ALL
SELECT 0
FROM dual
)
SELECT rnd, SIGN(rnd), CEIL(rnd/(1+ABS(rnd)))+FLOOR(rnd/(1+ABS(rnd))) "MySign"
FROM r

Result:

       RND  SIGN(RND)     MySign
---------- ---------- ----------
  -519.606         -1         -1
-657.62692         -1         -1
414.625079          1          1
736.175183          1          1
268.689074          1          1
-647.12649         -1         -1
338.192233          1          1
784.780876          1          1
-529.69184         -1         -1
-596.56803         -1         -1
         0          0          0

As you can see, “MySign” column perfectly matches SIGN column.

Comment:

WITH clause is needed to generate 10 random values in the range of -999 .. +999. “0” value is added to demonstrate a special case as it is unlikely that zero will be randomly generated.

 

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