, for example, in the figure above: NVL (p.mark, 0)p.mark is a value of type number. If the mark score is null, the value is 0; if not null, the value of p.mark is **
An NVL function is a null value conversion function
NVL (expression 1, expression 2)
If expression 1 is null, NVL returns the value of expression 2; otherwise, it returns the value of expression 1. The purpose of this function is to convert a null value (NULL) into an actual value. The value of its expression can be numeric, character, or date. But expressions 1 and 2 must have the same data type.
Logarithmic font: NVL (COMM,0);
To character NVL(TO_CHAR(COMM), ‘No Commission’)
NVL for date type (HireDate,’ 31-DEC-99′)
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