SELECT

The SELECT clause can also be used:

• arithmetic expressions
• aliases (alternative names) columns
• Concatenation
• literals

Arithmetic expressions

The arithmetic expression may be the column names, numeric constants and arithmetic operators:

   addition
- subtraction
* multiplication
/ sharing

example

SELECT ENAME, SAL FROM EMP * 12;

The expression is retained following priority actions:

1. multiplication
2. sharing
3. adding
4. subtraction

For example, in an arithmetic expression 250+12*34 is first calculated value of the expression 12*24 and the result is added value of the 250. Sequence of actions can be changed by using parentheses. For example, in an arithmetic expression (250+12)*34 first expression value is calculated 250+12, and the result is multiplied by the 34

Column Aliases

The default column headers can be replaced by other names, which are more significant.

Alias ​​is administered directly after the name of the column whose name we want to change. Spaces in the alias is not allowed, but you can create an alias with a space having a whole in double quotes.

example

SELECT ENAME Name , SAL*12 Salary, COMM Commision
FROM EMP;

Concatenation operator

Concatenation operator (||) allows you to combine a column with a column, literal, an arithmetic expression or a constant value. The arguments are combined to form one result column.

To connect the columns empno and ENAME and label them by way of EMPLOYEE, we write:

SELECT EMPNO|| ENAME EMPLOYEE
FROM EMP;

Literals

In addition to the columns in the SELECT list may contain literals (strings or numbers). Then for each line to be printed the same literal value:

EMPLOYEE SELECT ENAME, 'work in department', DEPTNO DEPARTMENT
FROM EMP;