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SQL Select Distinct
In SQL, the DISTINCT keyword is used to remove duplicate rows from the result set of a query.


What is DISTINCT in SQL?

  • DISTINCT eliminates duplicate records from the output of a SELECT statement.
  • It returns only unique values from a column or a set of columns.
  • DISTINCT can also be used with aggregate functions like COUNT(), SUM(), AVG(), etc.
  • It works on one or more columns, filtering out rows where all selected columns are identical.


Syntax:

SELECT DISTINCT column_name FROM table_name;

  • column_name: The name of the column you want to fetch unique values from.
  • table_name: The name of the table you are querying.


You can also apply DISTINCT to multiple columns:

SELECT DISTINCT column1, column2 FROM table_name;



Example: STUDENTS Table

Roll NoNameAge
101Nobita18
102Suneo16
103Shizuka18
104Gian23



Without DISTINCT - Duplicates Included

SELECT age AS Age FROM students;

Output:

Age
18
16
18
23

As you can see, age 18 appears twice because it is stored for two students.



With DISTINCT - Only Unique Ages

SELECT DISTINCT age AS Age FROM students;

Output:

Age
18
16
23

Here, duplicate age 18 is removed, and only unique ages are returned.



Key Point

  • Use DISTINCT when you want to avoid repeated values.
  • It filters entire rows, not just individual columns.
  • You can use it with single or multiple columns.
  • Helps keep your query results clean and readable.