Sunday, 15 May 2011

SQL ORDER BY

SQL ORDER BY

The ORDER BY clause is used in a SELECT statement to sort results either in ascending or descending order. Oracle sorts query results in ascending order by default.

Syntax for using SQL ORDER BY clause to sort data is:

SELECT column-list
FROM table_name [WHERE condition]
[ORDER BY column1 [, column2, .. columnN] [DESC]];

database table "employee";

For Example: If you want to sort the employee table by salary of the employee, the sql query would be.

SELECT name, salary FROM employee ORDER BY salary;

The output would be like

name salary
---------- ----------
Soumya 20000
Ramesh 25000
Priya 30000
Hrithik 35000
Harsha 35000

The query first sorts the result according to name and then displays it.

You can also use more than one column in the ORDER BY clause.

If you want to sort the employee table by the name and salary, the query would be like,

SELECT name, salary FROM employee ORDER BY name, salary;

The output would be like:

name salary
------------- -------------
Soumya 20000
Ramesh 25000
Priya 30000
Harsha 35000
Hrithik 35000

NOTE:The columns specified in ORDER BY clause should be one of the columns selected in the SELECT column list.

You can represent the columns in the ORDER BY clause by specifying the position of a column in the SELECT list, instead of writing the column name.

The above query can also be written as given below,

SELECT name, salary FROM employee ORDER BY 1, 2;

By default, the ORDER BY Clause sorts data in ascending order. If you want to sort the data in descending order, you must explicitly specify it as shown below.

SELECT name, salary
FROM employee
ORDER BY name, salary DESC;

The above query sorts only the column 'salary' in descending order and the column 'name' by ascending order.

If you want to select both name and salary in descending order, the query would be as given below.

SELECT name, salary
FROM employee
ORDER BY name DESC, salary DESC;

How to use expressions in the ORDER BY Clause?

Expressions in the ORDER BY clause of a SELECT statement.

For example: If you want to display employee name, current salary, and a 20% increase in the salary for only those employees for whom the percentage increase in salary is greater than 30000 and in descending order of the increased price, the SELECT statement can be written as shown below

SELECT name, salary, salary*1.2 AS new_salary
FROM employee
WHERE salary*1.2 > 30000
ORDER BY new_salary DESC;

The output for the above query is as follows.

name salary new_salary
---------- ---------- -------------
Hrithik 35000 37000
Harsha 35000 37000
Priya 30000 36000

NOTE: Aliases defined in the SELECT Statement can be used in ORDER BY Clause.

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