When we use a NULL value, it means they are unknown values. We can not consider them as empty strings or zero, which are valid values. In table creation, section details take into consideration setting them to acknowledge null values, or reject them. Essentially use a NULL or NOT NULL statement. This has applications in instances of missing record data like an ID number. Client characterized factors have an estimation of NULL until express task. Put away routine parameters and neighborhood factors permit setting an estimation of NULL. At the point when a neighborhood variable has no default esteem, it has an estimation of NULL.

BY Best Interview Question ON 13 Jan 2019