17.10 - Rules for WHEN Search Conditions - Advanced SQL Engine - Teradata Database

WHEN search conditions have the following properties:

• Can take the form of any comparison operator, such as LIKE, =, or <>.
• Can be a quantified predicate, such as ALL or ANY.
• Can contain a scalar subquery.
• Can contain joins of two tables.

  For example:

     SELECT CASE 
     WHEN t1.x=t2.x THEN t1.y 
     ELSE t2.y 
     END FROM t1,t2;
     

• Cannot contain SELECT statements.