DATABASE & SQL/PLSQL

Using TOP keyword

The TOP clause used with the SELECT statement. It is used to limits the number of rows returned in the result set

SELECT [TOP n] column_mame
FROM table_name
WHERE search_conditions 

'n'=number of rows that you want to retrieve.

Example

SELECT TOP 5 pub_id,pub_name,country
FROM publishers
WHERE country LIKE 'U%'
ORDER BY pub_id DESC

Returns all top 5 rows ,pub_id, pub_name and country,& from the publishers table in descending order & with respect to pub_id.

Using DISTINCT keyword

It also used to limit the result set. The DISTINCT keyword remove the duplicate row from the returned result set. It used with the SELECT statement.

SELECT  DISTINCTcolumn_mame
FROM table_name
WHERE search_conditions 

Example:

SELECT DISTINCT country
FROM publishers
WHERE city LIKE 'B%'

Return country name which started with a 'B' alphabet but no repetition, means no duplicate value of country.