Expressions

The select statement can also include one or more expressions, which allow you to manipulate the data that is retrieved.

select expression [, expression]... 
     from table_list 

An expression is any combination of constants, column names, functions, subqueries, or case expressions, connected by arithmetic or bitwise operators and parentheses. Expressions can include nested items (you can nest up to 32 functions in an expression).

If any table or column name in the list does not conform to the rules for valid identifiers, set the quoted_identifier option on and enclose the identifier in double quotes.

• Quoted Strings in Column Headings
  You can include any characters—including blanks—in a column heading if you enclose the entire heading in quotation marks.
• Character Strings in Query Results
  You can write queries so that the results contain strings of characters. Enclose the string in single or double quotation marks, and separate it from other elements in the select list with a comma.
• Computed Values in the select List
  You can perform certain arithmetic operations on date/time columns using the date functions.
• Arithmetic Operator Precedence
  When there is more than one arithmetic operator in an expression; multiplication, division, and modulo are calculated first, followed by subtraction and addition.