FunctionsReturningStrings ::=
"CONCAT" "(" StringPrimary "," StringPrimary ")" |
"SUBSTRING" "(" StringPrimary "," SimpleArithmeticExpression "," SimpleArithmeticExpression ")" |
"TRIM" "(" [["LEADING" | "TRAILING" | "BOTH"] [char] "FROM"] StringPrimary ")" |
"LOWER" "(" StringPrimary ")" |
"UPPER" "(" StringPrimary ")"