Operator Precedence in SELECT statement

*      /     +     -

• Multiplication and division take priority over addition and subtraction
• Operators of the same priority are evaluated from left to right 
• Parentheses are used to force prioritized evaluation and to clarify statements

Operator Precedence with example

SELECT ename,sal,12*sal+100 

FROM emp;

SELECT ename,sal,12*(sal+100)

FROM emp;

In the above examples parentheses makes a lot of differences in arithmetic calculation.

Arithmetic Expressions in SELECT statement

You may need to modify the way in which data is displayed, perform calculations, etc.

   Operator       Description

     +                     Add
      -                   Subtract
      *                  Multiply
      /                   Divide

Using Arithmetic Operators 

If we need to show Annual salary of employes then;

Another example:

Selecting Specific Columns

In the above example we 've selected only 3 columns from the table.

Errors: 

If we want to select column that is not in that table then SQL returns an error. 

Example:

Basic Select Statement or Selecting ALL Columns

Syntax of SELECT Statement

SELECT *|{[DISTINCT] column|expression [alias],....}
FROM table;

> SELECT identifies what columns
> FROM identifies which table

Selecting All Columns

SELECT * 

FROM dept;

Result: