1  Column_Select_Expressions

   A column select expression is a select expression that specifies
   a one-column result table in one row and can be nested
   within predicates and (if they specify a single value) value
   expressions. Column select expressions cannot specify a list of
   select items. You can only specify one value in a select list.

   Column select expressions are also called scalar expressions.

   SQL accepts column select expressions as arguments to IN and
   quantified predicates, and more generally as value expressions.

   o  As arguments to IN and quantified predicates, column select
      expressions specify a collection of values to which SQL
      compares a value expression. Therefore, column select
      expressions as arguments to those predicates can return one
      or more values.

   o  As a type of value expression, column select expressions
      specify a single value. Therefore, a column select expression
      used as a value expression should not return more than one
      value. If it does, SQL generates the following error:

      %RDB-E-MULTIPLE_MATCH, record selection criteria should identify
                             only one record; more than one record found

      If a column select expression used as a value expression
      returns zero rows, SQL evaluates the value expression as null.
      The data type of a column select expression used as a value
      expression is the same as the data type of the column select
      expression's select item.
 

2  Environment

   You can use column select expressions in interactive SQL or in
   host language programs.
 

2  Format

 col-select-expr =
 
 ---> select-expr ------->
 



 select-expr =
 
 -+-+->  select-clause  ------------+-+------+
  | +-> ( select-expr )  -----------+ |      |
  | +->   TABLE table-ref ----------+ |      |
  +------ select-merge-clause <-------+      |
    +------------------- <-------------------+
    +-+--------------------+--+------------------+--+--------------------+->
      +-> order-by-clause -+  +-> offset-clause -+  +-> limit-to-clause -+

 

2  Arguments
 

3  select-expr

   A column select expression is a select expression specifying only
   one value in the select list. See Select_Expressions for more
   information.