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Oracle Handling NULL values

Operations containing NULL are NULL, except concatenation


SELECT 3 * NULL + 5, 'Hello ' || NULL || 'world' FROM DUAL;

3*NULL+5 'HELLO'||NULL||'WORLD'


(null) Hello world

NVL2 to get a dierent result if a value is null or not


If the first parameter is NOT NULL, NVL2 will return the second parameter. Otherwise it will return the third one.

SELECT NVL2(NULL, 'Foo', 'Bar'), NVL2(5, 'Foo', 'Bar') FROM DUAL;

NVL2(NULL,'FOO','BAR') NVL2(5,'FOO','BAR')


Bar Foo

COALESCE to return the first non-NULL value


SELECT COALESCE(a, b, c, d, 5) FROM
 (SELECT NULL A, NULL b, NULL c, 4 d FROM DUAL);

COALESCE(A,B,C,D,5)


4

In some case, using COALESCE with two parameters can be faster than using NVL when the second parameter is not a constant. NVL will always evaluate both parameters. COALESCE will stop at the first non-NULL value it encounters. It means that if the first value is non-NULL, COALESCE will be faster.

Conclusion

In this page (written and validated by ) you learned about Oracle Handling NULL values . What's Next? If you are interested in completing Oracle tutorial, your next topic will be learning about: Oracle Columns of any data type can contain NULLs.



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