Take a database statement note: when the field is empty, assign the default value to the result

MySQL in ：IFNULL function

Format ：IFNULL( e1 , e2)

explain ：e1:    Represents the field name in the table

           e2 ： Indicates when the field e1 It's empty time , Assign a value of e2

for example ：

When age When there is no , The default value is 0

select ifnull(age,0) from student

Empathy

stay Oracle in , Out of commission IFNULL function , Need to use NVL Function instead of

Format ：

NVL( e1, e2 )

usage ： And IFNULL The functions are the same