An expression is a calculation or function that you include in a statement. The following statement calculates what the salaries for each employee in department 38 would be if each received a $500 bonus:
SELECT DEPT, NAME, SALARY + 500
FROM STAFF
WHERE DEPT = 38
ORDER BY 3
This result is:
DEPT NAME 3
------ --------- ----------------
38 Abrahams 12509.75
38 Naughton 13454.75
38 Quigley 17308.30
38 Marenghi 18006.75
38 O'Brien 18506.00
Note that the column name for the third column is a number. This is a system generated number, since SALARY+500 does not specify a column name. Later on this number is used in the ORDER BY clause to refer to the third column. Naming Expressions talks about how to give meaningful names to expressions.
You can form arithmetic expressions using the basic arithmetic operators for addition (+), subtraction (-), multiplication (*) and division ( /).
The operators can operate on values from several different types of operands, some of which are: