Oracle Database Handling NULL values COALESCE to return the first non-NULL value
Example
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.
