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We have a query that we know will return nulls for a certain column.  However, in the result set, sometimes we see null and sometiems it returns <Error> in the column when the value should be null.   When I hover over the <Error> value, the below message is displayed.
 

The presentation is to acquaint business users with Structured Query Language (SQL) and some interesting techniques to access their data with examples for using CASE; Subqueries and Correlated Subqueries; Types of SQL joins and how they are implemented on Teradata; facts about NULLs; Derived Table usage and other interesting optimizer information.