You can invoke SQL UDFs from within an SQL cursor. The rules for invoking an SQL UDF from within a cursor are the same as those for any other expression specified within an SQL cursor (see Teradata Vantage™ - SQL Stored Procedures and Embedded SQL, B035-1148 for details).
This example invokes an SQL UDF in the WHERE clause of a SELECT request in a cursor.
DECLARE ex1 CURSOR FOR SELECT * FROM t1 WHERE df2.common_value_expression(t1.a1, t1.b1) > 1 ORDER BY t1.a1;
This example invokes an SQL UDF in an UPDATE request in a cursor.
DECLARE ex3 CURSOR FOR UPDATE t1 SET b1 = df2.common_value_expression(t1.a1, t1.b1) WHERE c1 > 10;