Expressions are
combinations of symbols and operators that FedSQL evaluates and then
returns a single value. Expressions can be as simple as a single constant
or column or as complex as multiple expressions joined by an operator.
This chapter focuses
on three conditional expressions, CASE, COALESCE, and NULLIF, and
on <sql-expression>, a generic expression that defines all other
types of expressions.
Predicates specify
conditions that evaluate to either true, false, or unknown. They are
used most often in WHERE and HAVING clauses and in the FROM clause
in join conditions.