Oracle SQL Tutorials – Chapter 1 (Part 3 of 3)

ARITHMETIC OPERATORS

• Arithmetic operations can be used on the data which type is ‘date’ or ‘number’.
• The priority of the operators is like below ;

USAGE OF THE ARITMETHIC OPERATORS

• Let’s list the name, surname, salary and the new salary which is increased by 5% ; and give alias to them.

SELECT first_name NAME, last_name SURNAME , salary SALARY,(salary+salary*8/100)as NEW_SALARY FROM hr.employees;

THE NULL VALUE

• Null is a value that is unknown, unspecified or inconvenient.
• Null value is not zero(0) or whitespace. It is a common mistake.
• If a null value joins an arithmetic operation the result will be null.

• Let’s list the name, surname, salary, and commission if it exist, with the aliases.

SELECT first_name NAME, last_name SURNAME , salary SALARY, (salary*commission_pct)as COMMISSION FROM hr.employees;

THE CONCATENATION OPERATOR

• It combines columns or character sets with other columns.
• It is represented as double pipe : ||
• It creates a columns which is character type.
• Also , CONCAT command can used to concetanation.

• Let’s list the name, surname and salary with concatenation.

SELECT first_name||’ ‘||last_name AS “NAME SURNAME “,concat(‘Salary : ‘,salary) “SALARY” FROM hr.employees;

REPEATING ROWS

• The DISTINCT command is used to list the repeating rows just one time.

• Let’s list all departments of the company.

SELECT DISTINCT department_name FROM hr.departments;

VIEWING THE STRUCTURE OF TABLE

• The DESCRIBE command is used to view the table structure.
• DESC[RIBE] table_name;

• Let’s list the structure of the hr.employees table.

DESC hr.employees;

You can continue to read from this link ;

Oracle SQL Tutorials – Chapter 2 (Part 1 of 3)