A NULL value is a special marker used in SQL to indicate that a data value does not exist in the database. In other words, it is just a placeholder to denote values that are missing or that we do not know. NULL can be confusing and cumbersome at first.

What is NULL used for?

Null or NULL is a special marker used in Structured Query Language to indicate that a data value does not exist in the database.

When can a NULL value be used?

You know that the value should be zero. Think of NULL as “unknown.” You can use NULL values for any data type including integers, decimals, strings, or blobs. Even though many database administrators use NULL, they usually demand that NULLs are not used for numeric values.