SQL SELECT DISTINCT Keyword
The SQL SELECT DISTINCT keyword is used to fetch only unique (without duplicates) values or records.
It removes all the duplicate records from query results while fetching data from table.
It can filter only unique data for a single column value or an entire records from query result.
The SQL Distinct keyword will not ignore any NULL values from query result.
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SQL SELECT DISTINCT Syntax
The basic syntax of SQL SELECT DISTINCT statement is as follows:
SELECT DISTINCT column_name1 or expression1, column_name2 or expression2
FROM table_name;
- column_name or expressions - The table columns or calculations(formula) that you want to extract.
- tables - The tables that you want to fetch records from.
Sample Database Table - Books
| BookId | BookName | BookPrice | RelYear | DomainName | AuthorName |
|---|---|---|---|---|---|
| 1 | From Access To SQL Server | 145 | 2007 | Database | Geetha |
| 2 | Simply MySql | 70 | 2008 | Database | Siva Kumar |
| 3 | Understanding the New SQL | 75 | 2012 | Optimization | Padmavathi |
| 4 | SQL: The Complete Reference | 155 | 2012 | Optimization | Harish Karthik |
| 5 | Mastering Oracle SQL | 65 | 2008 | Optimization | Padmavathi |
| 6 | Mastering Oracle SQL | 105 | 2012 | Security | Dharan |
SQL SELECT DISTINCT Example - With Single Column
The following SQL SELECT statement selects all the unique data of "DomainName" from "Books" Table.
SELECT DISTINCT DomainName
FROM Books;
The result of above query is:
| DomainName |
|---|
| Database |
| Optimization |
| Security |
SELECT DISTINCT Example - With Multiple Column
The following SQL SELECT statement selects all the unique data of "DomainName" and "RelYear" from "Books" Table.
SELECT DISTINCT DomainName, RelYear
FROM Books;
The result of above query is:
| DomainName | RelYear |
|---|---|
| Database | 2007 |
| Database | 2008 |
| Optimization | 2008 |
| Optimization | 2012 |
| Security | 2012 |
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