SQL DISTINCT clause is used to remove duplicate records.
SELECT DISTINCT returns distinct(different) values.
DISTINCT can be used with aggregate functions: COUNT, AVG, MAX, MIN.
Syntax:
SQL SELECT DISTINCT based on one column
You can SELECT DISTINCT values from one column in a table.
Below is the syntax.
SQL SELECT DISTINCT based on multiple columns
You can SELECT DISTINCT values from multiple columns in a table.
Below is the syntax.
SELECT DISTINCT
Example:
Question 1:
From AdventureWorks2016 database, Select AverageRate column(field) from Sales.CurrencyRate table.
Query:
Result:
Question 2:
From AdventureWorks2016 database, Select Distinct AverageRate column(field) from Sales.CurrencyRate table.
Query:
Result:
Note:
Question 1 result pulled duplicate records (1.00) while in Question 2 result no duplicate record was pulled.
Total number of records pulled
Question 1 – 13532 rows
Question 2 – 6127 rows
In summary, the DISTINCT keyword is very helpful when analyzing data by removing duplicates and eliminating data redundancy.
