16.20 - Example: Searching a Table That Might Contain Nulls - Teradata Database

Teradata Vantageā„¢ - SQL Functions, Expressions, and Predicates

prodname
Advanced SQL Engine
Teradata Database
vrm_release
16.20
created_date
March 2019
category
Programming Reference
featnum
B035-1145-162K

You must be careful when searching a table that might contain nulls. For example, if the EdLev column contains nulls and you submit the following query, the result contains only the names of employees with an education level of less than 16 years.

   SELECT Name, EdLev 
   FROM Employee 
   WHERE (EdLev < 16) ;

To ensure that the result of a statement contains nulls, you must structure it as follows.

   SELECT Name, EdLev 
   FROM Employee 
   WHERE (EdLev < 16) 
   OR (EdLev IS NULL) ;