`information_schema.parameters.parameter_default`

mysql

type: CHARACTER_DATA NULL

Note:

The default expression of the parameter, or null if none or if the function is not owned by a currently enabled role.

10-15

type: CHARACTER_DATA

Note:

The default expression of the parameter, or null if none or if the function is not owned by a currently enabled role.

9.4-9.6

type: NULL

Note:

Always NULL.